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Summary. Halicarcinus lacustris is a small crab inhabiting inland waters in south-eastern. Australia, New Zealand, and Lord Howe and Norfolk Islands.
THE ECOLOGY AND DISTRIBUTION O F HALICARCINUS LACUSTRIS (BRACHYURA: HYMENOSOMATIDAE) IN AUSTRALIAN INLAND WATERS

[Manuscript received March 28,19691 Summary Halicarcinus lacustris is a small crab inhabiting inland waters in south-eastern Australia, New Zealand, and Lord Howe and Norfolk Islands. The Victorian distribution was investigated with reference to salinity. In the field the species occurs over a salinity range of 0.1-9.6%, (although scarce in fresh waters), despite a tolerance of 0.0-36.3%, shown by adults in the laboratory. This restricted distribution is attributed to physiological and ecological factors. Ecological notes are included on microhabitat, associated species, food, and the breeding cycle. Consideration is given also to the origins and overall distribution of the species. It is suggested that H. lacustris rafted across the Tasman Sea, after having evolved in south-eastern Australia.

Apart from the high degree of endemicity shown by the fauna of Australian inland waters, relatively speaking it appears that a larger proportion of this fauna is directly derived from marine forms than is the case elsewhere in the world. Among those faunal elements having close marine affinities is Halicarcinus lacustris (Chilton 1882) (Fig. l), and an investigation of the distribution and certain aspects of the biology of this species in Victoria forms the basis of the present paper.

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Halicarcinus lacustris belongs to the Hymenosomatidae, a family of some 50 species of Indo-Pacific distribution, all but six? being marine or estuarine in habit.

* Department of Zoology, Monash University, Clayton, Vic. 3168. t Hymenosoma orbiculare Desm., a typically estuarine form, may also occur in coastal freshwater lakes as happens in Natal, South Africa (Allanson et al. 1966). Aust. J. mar. Freshwaf. Res., 1969,20,163-73

19, Mt. Emu Ck., Darlinglon, H.H.; 20, Mt. Emu Ck., Skipton, G.H.; 21, Gnarkeet Ck., Lismore, H.H.; 22, Woady Yallock R., Cressy, H.H.; 23, L. Colac, south shore (Fulton and Grant 1902);* 24, Borongarook Ck.. Colac.. P.H.: . 25, L. Modewarre, east shore; 26, Moorahool R. (Fulton and Grant 1902);t 27, Hovell's Ck., Lara; 28, Hovell's Ck., Bacchus Marsh Rd.; 29, Little R., P.H.; 30, Werribee R., P.H.; 31, Skeleton Ck., Laverton, P.H.; 32, Yarra R., Burnfey (Anon. 1915);* 33, Lang Lang R., P.H.; 34, Fraser's Ck., Oberon Bay (Kershaw 1906); 35, U ~ a m e dCk., adjacent to 34; 36, Unnamed Ck., Little Waterloo Bay.

Fig. 2.-Victorian distribution of Halicarcinus lacustris. Crab localities; 0 other apparently suitable localities visited during 1966-68, yet without crabs. Place names in key refer to nearest landmarks; G.H., H.H., P.H., and S.G.H. refer to Glenelg, Hamilton, Prince's, and South Gippsland Highway crossings respectively. * Previously published records. -F Locality not specified by authors.

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KEY

1, Fitvoy R.. Heywood, P.H.; 2, Drainage channel near L. Condah; 3, Eumeralla R., Yambuk, P.H.; 4, Moyne R., Port Fairy, P.H. 5, Moyne, R., Koroit; 6, Hopkins R., Allansford, P.H.; 7, Hopkins R., Hexham, H.H.; 8, Hopkins R., Chatsworth; 9, Hopkins R., Wickliffe; 10, Hopkins R., Ross Bridge; 11, Salt Ck., Hexham, H.H.; 12. Salt Ck., Lake Bolac; 13, Lake Bolac. west shore; 14, Fiery Ck., Lake Bolac; 15, Fiery Ck.. Streatham, G.H.; 16. Mt. Emu Ck., Panmure, P.Q. 17, L. Elingamite, east shore; 18, Mt. Emu Ck., Terang, P.H.;

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Five of these six species have been recorded from one locality each: H. wolterecki Balss 1934 in the Philippines, H. pilosus (A. Milne Edwards 1873) in New Caledonia, H. angelicus Holthuis 1968 in Papua, Neorhynchoplax intvoversus (Kemp 1917) in China, and N . kempi (Chopra and Das 1930) in Iraq. Little is known of their biology ~ is, however, more other than that they occur in fresh waters. ~ a l i c a r c i nlacustris widespread, and has been recorded from south-eastern Australia (Victoria: Fulton and Grant 1902; Kershaw 1906; Anon. 1915; South Australia: Hale 1926, 1927; Tasmania: Chilton 1919; Guiler 1952), the North Island of New Zealand (Chilton 1882, 1906, 1912; Powell 1947), Lord Howe Island (Etheridge 1889), and Norfolk Island (Fulton and Grant 1902). There are also unpublished records from these areas (see Lucas 1968), and from King Island (Victorian Museum Collection, and G. W. Brand, personal communication). In these regions H , lacustris has been generally regarded as a "freshwater" form, although precise salinity data are lacking. The biology of the species has been neglected aside from recent work by Lucas (1969), who has elucidated aspects of the growth and reproduction. Halicarcinus lacustris was originally described by Chilton (1882) as Elamena (?) lacustris, from a single specimen found in Lake Pupuke (or Takapuna), near Auckland, New Zealand. Subsequently Chilton (1883), using further specimens, enlarged on his description and transferred the species to the genus Hymenosoma Desm. The generic transference to Halicarcinus White was effected by Kemp (1917). Material from Victoria, New Zealand, and Norfolk Island was compared by Fulton and Grant (1902) who, although finding some slight but inconstant regional differences, concluded the material was conspecific. This conclusion is further supported by Chilton (1906, 1915, 1919) and Tesch (1918). Halicarcinus lacustris therefore is the only hymenosomatid common to the Australian mainland and New Zealand. This is unusual since in these two regions the hymenosomatid faunas in particular, and the brachyuran faunas in general, are highly endemic (Bennet 1930; Montgomery 1931 ; Gordon 1966).

Halicarcinus lacustris has previously been reported in Victoria from Lake Colac, the Moorabool and Yarra Rivers, and Fraser's Creek. It is now possible to extend considerably this known distribution; the results of a number of collecting trips during 1966-68 are detailed in Figure 2. As this figure shows, the species is widely distributed in the river and lake systems of the Western District, and also occurs east of Melbourne, in the Lang Lang River, and on Wilson's Promontory. However, it seems to be absent from the rest of Victoria (Fig. 2), although there are large numbers of apparently suitable streams in the Gippsland region (eastern Victoria). This distribution is evidently a consequence of both present ecological conditions and past physiographic events. The role of physiographic changes is revealed by considering localities in terms of composite drainage systems. Thus in the Western District the s~eciesis found throughout the Hopkins System (Hopkins River, Mt. Emu, Salt and Fiery Creeks, and Lakes Bolac and Elingamite), and the Port PhillipWestern Port System (Little, Werribee, Yarra, and Lang Lang Rivers, and Hovell's

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and Skeleton Creeks). Furthermore, the widespread occurrence of the species in Lakes Colac and Modewarre, the Woady Yallock River, and the Borongarook and Gnarkeet Creeks, may be accounted for by considering the common progenitor of this group of localities, an endorheic basin formerly occupied by a more extensive Lake Corangamite (Currey 1964). The basaltic plains of the Western District were under the influence of volcanic activity from Pliocene to Recent times (Ollier and Joyce 1964). Such plains are typically areas of immature drainage systems, the river courses being in a constant state of flux; processes of stream capture and diversion are characteristic of such patterns. These fluctuations probably provided the dispersal means which gained H. lacustris its present widespread distribution in the Western District. Furthermore, the H. lacustris localities bordering Port Phillip and Western Port are evidently the isolated tributaries of a formerly confluent river system. The system was betrunked by submergence of parts of the Victorian coastal plains caused by the rise in sea level during the melting of the Pleistocene glaciers (Hills 1959). This rise in sea level coupled with land movements also caused the severance of Tasmania from the mainland, isolating populations of H. lacustris on Wilson's Promontory, King Island, and Tasmania. 111. SALINITYTOLERANCE (a) Field Investigations An important feature of the distribution of H. lacustris is that, at least in Victoria, the species is mainly restricted to slightly saline waters. This is indicated by Figure 3, which represents salinity data for most localities from which crabs were collected. Salinity values were derived from conductivity determinations on water samples brought back to the laboratory. The conversions of conductivity firstly to total dissolved solids, and secondly to salinity, were done using the conversion factors of Williams (1966), and Bayly and Williams (1966) respectively. Most data in Figure 3 derive from more than one visit to a particular locality. Of these localities, one in particular, Skeleton Creek (No. 31), is of interest in showing a considerable seasonal fluctuation in salinity, viz. from a minimum of 1 .4x0in December 1966, to a maximum of 9.6% in March and April 1967. Perhaps significantly, Skeleton Creek harbours certainly the densest crab population that the author has encountered. Thus, H. lacustris was found in salinities between 0.1 and 9.6%,, but was most commonly encountered within the range 1-6%0,that is in fresh (but very hard) waters to slightly saline waters. Single populations seem able to withstand considerable fluctuations in salinity. (b) Laboratory Inuestigations

The aim of the laboratory investigations was to elucidate the possible influence of salinity in determining the field distribution of the species. An experimental sample of crabs was collected from Skeleton Creek near Laverton, Victoria. In the laboratory, this sample was subdivided into three groups of uniform age distribution,

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each group containing 25 males and 25 females (i.e. 50 crabs per group). Each group was kept in a white enamel pie-dish (26 by 23 by 4 cm), with an air supply, a Perspex cover to minimize water loss by evaporation, and a square of netting to serve as a substrate. The crabs were fed on brine shrimp nauplii or eggs. The experiment was performed in a constant temperature room at 18 0.5Oc, with a 12-hour photoperiod.

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Salinity

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(O/oo)

Fig. 3.-Salinity data @ec. 1966 to Sept. 1967) for a number of Victorian Halicarcinus lacustvis localities. Most localities were visited in summer and winter to reveal the degree of seasonal salinity fluctuations. For key see Figure 2.

Seven days were allowed for laboratory acclimatization. At the commencement of the experiment one group was transferred to a dish containing water of lower salinity ("down" group), another into water of higher salinity ("up" group), while the remaining group (control) was maintained in natural water of 8.6%, salinity. A period was allowed for acclimation to the changed salinity, and then the two experimental groups were moved to another dish containing water of lower or higher salinity, respectively. The control water was exchanged for "fresh" natural water with every alternate changeover for the stressed populations. The acclimation periods were not constant, but varied from 2 to 5 days depending on the degree of stress. These periods were considered more than adequate since studies on other aquatic animals generally indicate that acclimation occurs rapidly (in the first 12 hr), and for most species is virtually complete in a few days (Prosser and Brown 1961). Experimental solutions were prepared by dilution or concentration of Skeleton Creek water. The criterion for death was taken as the failure to respond to a probe lifting the abdomen; invariably in healthy crabs this evoked a defensive motor response.

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The responses of the experimental groups to progressive alterations in salinity are shown in Figure 4. It is most meaningful to speak in terms of the tolerance of the "average" individual. This is best expressed by computing the stress required to kill 50 % of the population (see Fig. 4). The median tolerance limits for H , lacustris (at 18"c)were 0.0 and 36.3%,, demonstrating a marked euryhalinity.

Fig. 4.-Computation

of median salinity tolerance limits. Limits of tolerance (*): 0.0 and 36.3%,. Arrow denotes control salinity (8.6%,). Mortality scale is corrected to account for control mortalities. I -20 -2.0

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(c) Discussion Although caution is needed when extrapolating laboratory results to field situations, the very marked difference between the wide range of salinity tolerated by adult crabs, and the narrower range within which H. lacustris has been found in the field, suggests that such a difference has some significance. It is possible that the species is absent from natural waters of salinity greater than about lo%, because of the restrictive action of salinity (and temperature) on reproductive activities. Studies of the effects of salinity on aquatic animals have shown that tolerance may be different in the various phases of the life cycle. In many species it is most narrow during early ontogeny, then increases somewhat, and finally decreases in the senile adult (Kinne 1964). It seems reasonable to assume that this same general relationship applies to H. lacustris, as it does to H. australis, a related estuarine species (Lucas 1968). Despite this restriction, reproduction in H. lacustris is nevertheless remarkably tolerant of salinity; berried females were noted over a range of from 0.4to 7.O%,. The apparent absence of the species in the fresh waters of the Gippsland region remains so far unexplained. The Gippsland streams differ significantly from those of the Western District in a number of important respects, the most fundamental being catchment relief. The Gippsland rivers rise in the Eastern Highlands, which are normally snow-covered during winter. The river catchments of the Western District, on the other hand, are of much lower relief, and do not have a seasonal snow cover. This geographical difference leads to concomitant differences in the volumes of water carried, temperatures, and salinities. Gippsland rivers carry cooler waters of much larger volume and with greater seasonal periodicity in flow rates (State Rivers and Water Supply Commission, Victoria 1967) than do rivers of the Western District. Gippsland rivers, moreover, have salinities invariably less than 0.2%,; Western District rivers commonly have salinities of about 4%, (Webster 1965). This situation

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is a consequence of various physiographic and climatic conditions (Cope 1958; Bayly and Williams 1966). These marked physicochemical differences between the surface waters of eastern and western Victoria have profound effects on the biotas, as evidenced by H, lacustris. Certainly, more intensive studies of this situation are desirable. 1V. FURTHEROBSERVATIONS (a) Microhabitat Halicarcinus lacustris occurs in lakes and slowly-flowing streams, which are often of a shallow swampy nature. Such localities mostly have a substratum of deep mud or organic silt. In general crabs are most commonly found clinging either to submerged macrophytes or the root systems of emergent macrophytes. They also occur on the sheltered surfaces of submerged rocks in places where debris from road constructions litter the stream or lake bed. (b) Associated Biota A frequent macrophytic associate of H. lacustris is the yellow-flowered waterbutton, Cotula coronipifolia L., which commonly grows out over the surface of the water, sending down dense roots which serve as a microhabitat for a variety of animals, including H. lacustris. This distinctive plant often serves as an indicator for the presence of crabs. Other associated macrophytes include Phragmites communis Trin., Ruppia maritima L., Potamogeton sp., and Myriophyllum spp. Among the commonly associated macroscopic animals are the bivalve Corbiculina angasi Prime and amphipods (Austrochiltonia spp.). The atyid prawn Paratya australiensis Kemp occurs in most freshwater localities, but is absent from waters of about 3%"and upwards. Another species, P. curvirostris (Heller), has been reported as a permanent associate of H. lacustris in overseas localities (Chilton 1915 ; Paramanov 1960). (c) Food The food of H. Iacustris was investigated by examining gastric mill contents. Three field collections of about 50 individuals each were made from Skeleton Creek on different dates for this purpose. However, the number of crabs with identifiable mill contents in any one of these collections was low (about 10). The results indicated that H. lacustris, like most crabs, is omnivorous. Mill contents comprised either amphipod remains (Austrochiltonia spp.), algal strands, root fibres (Cotula coronipifolia), but mostly indeterminate mush. This latter component is not surprising in view of the efficiency of most decapod gastric mills.

(d) Predators A factor which may be of considerable importance in determining the distribution of H. lacustris is the relative intolerance to salinity of its possible freshwater predators. It is known that fish frequently prey upon marine or estuarine hymenosomatids in New Zealand (Graham 1938) and also Tasmania (J. S. Lucas,

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personal communication), and freshwater crayfish certainly do on H. lacustris in the laboratory. Field observations strongly suggest that H. lacustris and parastacid crayfish are mutually exclusive in their Victorian distributions. This is apparently because crayfish (i.e. truly aquatic crayfish) are averse to even slightly saline waters (E. F. Riek, personal communication). Thus the predatory components of freshwater communities may be of some importance in the ecology of H , lacustris. Competition is unlikely to be a significant factor considering the broad niche occupied by the species. (e) Breeding Cycle Halicarcinus lacustris, in common with most freshwater decapods, hatches its young at a relatively advanced stage of development. From ovulation to hatching under laboratory conditions takes 55 days (20°c), compared with 13 days (20°c) for the estuarine H. paralacustris (Lucas 1968). However, little is known of ecological regulation of the breeding cycle. The number of broods hatched by an individual in one season is about three. Qualitative field collections from Skeleton Creek (1966-67) showed that berried females appear in winter (July), and persist until midsummer (February). By midspring (October), two months after the first ovulation, the first juveniles appear. Females normally ovulate again within a few days of hatching a brood, so that the influx of juveniles continues until mid-autumn (April). The population, which at this stage is largely made up of immature individuals, then enters a winter maturation phase.

A series of crossing experiments by Lucas (unpublished data) has established the existence in Australia of an estuarine sibling species of H. lacustris, viz. H. paralacustris. The most significant morphological difference between the two species is concerned with the female reproductive apparatus. Reproductively, the species are quite distinct; whereas free larval development is completely suppressed in H. lacustris, in H, paralacustris development involves the three zoeal stages typical of Hymenosomatidae. Consequently the eggs of H. lacustris are considerably larger, more yolky, and fewer in number than those of H. paralacustris. Lucas in fact considers the evolutionary precursor to H. lacustris to be an indirect development form similar to H. paralacustris. Present fossil evidence places the origin of the Oxyrhyncha, which includes the Hymenosomatidae, during the Tertiary (M. F. Glaessner, personal communication). A number of facts point to a more recent origin for H. lacustris, contrary to the view of Chilton (1915), who considered the distribution of the species reflected former land connections. In the first place, the limited degree of genetic compatability (Lucas 1969) and in addition the close morphological similarity between the two sibling species suggest that H. lacustris has not had a prolonged evolutionary history. Secondly, the euryhalinity of H. lacustris is opposed to the tendency for long-isolated freshwater species to be oligohaline in character (Hutchinson 1967). Thus the degree of phsyiological emancipation from the sea which an organism

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living in fresh-water displays may be considered an indication of its evolutionary age. H. lacustris still retains the wide salinity tolerance characteristic of its estuarine relatives. The distribution of the estuarine H. paralacustris, although imperfectly known, extends from Brisbane to the western Victorian coast (Lucas 1969). There seems little doubt, however, on the basis of Gordon's (1966) intensive survey, that this species does not occur in New Zealand. This is one objection to a suggestion that the existence of H. lacustris on six isolated land masses may be the result of simultaneous derivations from a widespread common ancestor. The occurrence of H. lacustris on the Australian mainland, on King Island, and Tasmania is explained by the existence of Pleistocene land bridges, whereas land connections are not a tenable explanation for the occurrence of the species on both sides of the Tasman Sea (Fleming 1957; Lucas 1969; cf. however Chilton 1915). The alternative is that H, lacustris originated in south-eastern Australia and dispersed across the ocean, in which case some adventitious mode of transport must have been involved. Lucas (1969) suggests that H. lacustris may have reached New Zealand on the feet or feathers of waterfowl. Another explanation is that H , lacustris reached New Zealand by rafting across the ocean. Thus crabs may have been transported out to sea on floating debris, and carried to northern New Zealand and the island localities by the East Australian Current. Data collected during oceanographical cruises by the CSIRO have shown that this current is the main component of a complex system of oceanic circulation in the region of the Tasman Sea (Hamon 1965; Highley 1967). Although the circulation patterns are too variable and complex to permit clearly defined paths to be interpreted, there is a general movement of surface water eastwards from the Australian coast towards and to the north of New Zealand (Woodhead 1968). The general paths of the ocean currents therefore closely correspond to the distribution of H. lacustris. VI. ACKNOWLEDGMENTS This study was carried out as part of a B.Sc.(Hons.) degree at Monash University. The author is indebted to his supervisor, Dr W. D. Williams, for encouragement and for criticism of earlier drafts of this paper. Grateful acknowledgn~entis made also to Dr J. S. Lucas, Townsville University College, for allowing the author to quote an unpublished MS, for valuable advice, and for reading the present manuscript, and to Mrs M. J. Melrose (nCe Gordon), Auckland, New Zealand, for permission to quote from an unpublished thesis. Thanks are due to artists Miss D. McCay (Fig. 1) and Mrs D. Troon (Figs. 2-4) for assistance. VII. REFERENCES ALLANSON, B. R., HILL,B. J., ROLTT, R. E., and SCHULTZ,V. (1966).-An

estuarine fauna in a freshwater lake in South Africa. Nature, Lond. 209, 532-3. ANON.(1915).--Remarks on exhibits. Victorian Nat. 31, 109-10. BALSS, H. (1934).-Mitteilungen von der Wallacea-Expedition Woltereck. Mitteilungen XI: die Dekapoden. 2001. Anz. Leipzig 106, 177-84. BAYLY,I. A. E., and WILLIAMS, W. D. (1966).-Chemical and biological studies on some saline lakes of south-east Australia. Aust. J. mar. Freshwat. Res. 17, 177-228.

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BENNET,E. W. (1930)-Notes on New Zealand Brachyura and related crustaceans. Rec. Canterbury Mus. 3,255-61. CHILTON, C. (1882).-Additions to the New Zealand Crustacea. Trans. N.Z. Inst. 14, 171-4. CHILTON, C. (1883).--Further additions to our knowledge of the New Zealand Crustacea. Trans. N.Z. Znst. 15, 69-86. CHILTON, C. (1906).-Notes on some Crustacea from the freshwater lakes of New Zealand. Proc. zool. SOC.Lond. 76, 702-5. CHILTON, C. (1912).-Miscellaneous notes on some New Zealand Crustacea. Trans. N.Z. Znst. 44, 128-35. CHILTON, C. (1915)-A freshwater crab, and its distribution in Australia and New Zealand. Trans. N.Z. Inst. 47, 316-20. CHILTON,C. (1919).-Note on the occurrence in Tasmania of the freshwater crab, Hymenosoma lacustris, Chilton. Pap. Proc. R. Soc. Tasm. 1919, 93-5. CHOPRA, B., and DAS,K. N. (1930).-Further notes on Crustacea Decapoda in the Indian Museum. I. On two new species of hymenosomatid crabs, with notes on some other species. Rec. Zndian Mus. 32, 413-29. COPE,F. (1958).-Catchment salting in Victoria. 88 pp. Soil Conservation Authority, Victoria. CURREY, D. T. (1964).--The former extent of Lake Corangamite. Pvoc. R. Soc. Vict. 77, 377-86. ETHERIDGE, R. (1889).--Lord Howe Island: its zoology, geology, and physical characters. Mem. Aust. Mus. 2. FLEMING,C. A. (1957).-Trans-Tasman relationships in natural history. pp. 228-46. In F. R. Callaghan (Ed.) "Science in New Zealand." (Reed: Wellington.) FULTON,S. W., and GRANT,F. E. (1902).-Some little-known Victorian decapod Crustacea with descriptions of new species, no. 11. Proc. R. Soc. Vict. 15, 59-68. GORDON, M. J. (1966).-Contributions to the systematics and ecology of the New Zealand Hymenosomidae (Crustacea Brachyura). M.Sc. Thesis, University of Auckland. GRAHAM, D. H. (1938).-Food of the fishes of Otago Harbour and adjacent sea. Trans. R. Soc. N.Z. 68,421-36. GUILER,E. R. (1952)-A list of the Crustacea of Tasmania. Rec. Queen Vict. Mus. 111, 15-44. HALE,H. M. (1926).-Note signed "H.M.H." S. Aust. Nut. 7, 69. HALE,H. M. (1927).-"The Crustaceans of South Australia. Part I." (Govt. Printer: Adelaide.) HAMON, B. V. (1965).-The East Australian Current, 1960-1964. Deep Sea Res. 12, 899-921. HIGHLEY, D. (1967).-Oceanic circulation patterns off the east coast of Australia. CSIRO Aust. Div. Fish. Oceanogr. Tech. Pap. No. 23. HILLS,E. S. (1959)-"The Physiography of Victoria." (Whitcombe and Tombs: Melbourne.) L. B. (1968),-On Hymenosomatidae (Crustacea Decapoda Brachyura) from fresh water, HOLTHUIS, with the description of a new species. Beaufortia 15 (195), 109-21. HUTCHINSON, G. E. (1967).-"A Treatise on Limnology." Vol. 2. (Wiley: New York.) KEMP,S. (1917).-Notes on Crustacea Decapoda in the Indian Museum. X. Hymenosomatidae. Rec. Zndian Mus. 13, 243-79. J. A. (1906).-Excursion to Wilson's Promontory-general zoology. Victorian Nut. 22, KERSHAW, 206-7. KINNE,0.(1964).-The effects of temperature and salinity on marine and brackish water animals. 11. Salinity and temperature-salinity combinations. Oceanogr. mar. Biol. Ann. Rev. 2, 281-339. L u c ~ sJ. , S. (1968)-The biology of the Australian species of the genus Halicarcinus White. Ph.D. Thesis, University of Western Australia. Lrrcas, J. S. (1969).-Breeding experiments to distinguish two sibling species of Halicavcinus (Crustacea, Brachyura). J. 2001.157 (in press). MILNEEDWARDS, A. (1873).-Recherches sur la faune carcinologique de la Nouvelle-Caledonie. Deuxieme partie. Nouv. Archs Mus. Hist. nut., Paris 9, 155-332. MONTGOMERY, S. K. (1931)-Report on the Crustacea Brachyura of the Percy Sladen Trust Expedition to the Abrolhos Islands under the leadership of Professor W. J. Dakin, D.Sc., F.L.S., in 1913; along with other crabs from Western Australia. J. Linn. Soc. (Zool.) 37, 405-65.

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OLLIER,C. D., and JOYCE,E. B. (1964).-Volcanic physiography of the western plains of Victoria. Proc. R. Soc. Vict. 77, 357-76. PARAMANOV, S. J. (1960).-Lord Howe Island, a riddle of the Pacific. Part 11. PaciJ: Sci. 14, 75-85. POWELL, A. W. B. (1947)-"Native Animals of New Zealand." (Unity Press: Auckland.) Animal Physiology." (Saunders: PROSSER,C. L., and BROWN,F. A. (1961)-"Comparative Philadelphia.) VICTORIA(1967).-"River Gaugings to 1965." STATERIVERSAND WATERSUPPLYCOMMISSION, (Govt. Printer: Melbourne.) TESCH,J. J. (1918).-Hymenosomidae, Retroplumidae, Ocypodidae, Grapsidae, and Gecarcinidae. The Decapoda Brachyura of the Siboga Expedition, I. Siboga Exped. Monogr. 39c, 1-148. WEBSTER, R. G. (1965).-The salinity of surface waters in Victoria, Australia. Proc. 2nd Australas. Conf. Hydrauls. Fluid Mech., B7-32. W. D. (1966)-Conductivity and the concentration of total dissolved solids in Australian WILLIAMS, lakes. Aust. J. mar. Freshwat. Res. 17, 169-76. WOODHEAD, P. M. J. (1968).-Sea surface drift between central Queensland and New Zealand. Aust. J. Sci. 31, 195-6.