HORN EXPEDITION — SUMMARY. 195 



Cri/sfaccn. — Amongst land and frfsli-wator forms the nioro important aro the 

 following : — Lopidurus is found in the oastorn coastal district from New South 

 Wales through Victoria to Tasmania and i-eaches westwards into the coastal parts 

 <(f Hnuth Australia. The internal area of the continent, from the inland parts of 

 (.Jueenslanfl, New South Wales and Victoria on the east side I'ight across to West 

 Australia, is chai'acterised by the aljsence of Lepidurus and the presence of Apus. 



Amongst Brachyura tlie land crab Tclpluisa transversa is a north-eastern form 

 which has spread aci'oss to the Centre. Amongst the Macrura one foini {Asiacopsis 

 bicarinalits) extends over practically the whole of the continent, occuri-ing right in 

 the Centre and all along the eastern and south-eastern coast from (Queensland to 

 Victoi'ia. Tasmania is distinguished by the presence of distinct species i^A. 

 fraitklinii)^ but the most impoi-tant fact is tlH> presence of a genus of burr<iwing 

 la,n(l craylish, En_i;(riis, confined to a,nd characteristic of the s<Hith-east and 

 Tasmania, and not even extending so far north along the east coast as New South 

 Wales. 



Mollusca. — In the land and freshwater mollusea we can distinguish (1) a 

 north eastern or (.Queensland group. With regard to this Mr. Cooke* says, "The 

 strip of coast-line from Cape York to the Clarence River stands apart from (he 

 r(>st of Australia., and is closely connected with New (.uinea. There can be little 

 doubt that is has been colonised from the latter country, since an elevation of even 

 ten fathoms would create a wide bridge Iwttween the two. Many of the genera 

 are quite strange to the rest of Australia." In this area the more important 

 genera, ar'e Hai/ra, which h(n'(^ reaches its maxiuni, Rliytida^ Cliloriiis, Plauispira, 

 Panda, Thcrsitcs, Sfaiot^^yra, amongst slugs Janella and amongst fresh-water forms 

 I si dor a. 



It is from this region that the species of Iladra, Chlari/is, Pla/iispira, T/icrsitcs, 

 Sfaiflgyra and the ancestors of Isidordia must have passed across to the centre 

 where they have since been isolated. This would appear to .show that the 

 Rliytidida\ which are now established in the noi'th and of which, as Mr. Hedley 

 .says, " originating in Antarctica," one group '' established itself in Tasmania and 

 marched in force to Cape York and e\'en crossed to Mount Owen Stanley in New 

 Cuinea," had not reached far enough north in time to allow them to pass across 

 to the centre. 



(2). A restricted West Australian group represented by species of Lipariis, 

 Pupa, Si/cciiiea, anrl the group Rhas;ada amongst Helices. 



* " Mollnsos and Ri'.afliipnds. " r.aiiilnidjfc N.at. Hist., p. 322. The infnrmatrioti with rcu;anl to the disti-iliutii>ii 

 of the Molhisc.% referred to, e.\cei)t thosi' of Central Australia, is taken from this worl;. 



*1:3a 



