370 AUSTRALIAN REGION 



whole of the region excepting New Zealand and the adjacent 

 islands) is determined by the influence of the Antarctic Drift, 

 which washes the whole of the southern coasts of Australia, and 

 runs strongly northward between Australia and New Zealand. 

 The E. Australian warm current from the north is checked at 

 Sandy Cape by this cold ciu-rent, and flows off to New Zealand, 

 the western shores of which island are consequently mucli warmer 

 than the eastern. On the western coast of Australia the 

 Antarctic Drift has less force, and tropical genera accordingly 

 range some 7 degrees farther south on the western than on the 

 eastern coasts. 



The characteristic genera are Valuta (of which half the known 

 species occur on Australian coasts -^ ), Cominella, Siph onalia, 

 Strutliiolaria, Risella, Fhasianella, a number of genera belonging 

 to the Trochidae, e.g. Liotia, Clanculus, Euchelus, Thalotia, 

 Menchus, Trochocochlca, Zizyphinus, JBankivia; Trigonia, Myodora, 

 Myocliama, Solenomya, Ep)hippodonta, Anapa, Mylitta, Mcsodesma, 

 and Chamostrea. Trigonia, originally discovered as a recent 

 form in Sydney Harbour (p. 65), is not peculiar to that locality, 

 occurring also off Cape York, West Australia, and Tasmania. 



(2) The Neozealanian Stih-region includes New Zealand, with 

 the outlying islands (Chatham, Auckland, and Campbell Is.). 



As many as 455 species (Cephalopoda, 8 ; Gasteropoda, 311 ; 

 Scaphopoda, 2 ; Pelecypoda, 134) have been enumerated by Professor 

 F. W. Hutton as occurring within the sub-region, of which only 

 64 are found elsewhere, the proportion of peculiar species being 

 thus nearly 86 per cent. New Zealand therefore is, in its marine, 

 no less than its land Mollusca, greatly isolated. 



The characteristic genera are Anthora, Cryptoconchus, and 

 Vanganella, which appear to be quite peculiar, Troplion, Cominella, 

 Euthria, most of the Trochidae also characteristic of S. Australia, 

 Haliotis, Patella; Taria, Mesodesma, Mylitta, Zenatia, Standella, 

 and Myodora. 



D. The American Region 



includes the entire coasts of North and South America with the 

 adjacent islands, south of Cape Avinoff on the western, and south 



^ A full account of the distribution of Valuta is given by Ci'osse, Journ. cle Conchyl. 

 (3) xix. p. 263. 



