GASTROCOPTA, AUSTRALIA. 155 



of the peristome. The description is slightly abbreviated from 

 Gassies, and the figure copied from his plate. Both are evi- 

 dently incomplete. I have not seen specimens. Perhaps re- 

 lated to the Australian G. hedleyi, but certainly the descrip- 

 tion and figure strongly suggest G. contracta (Say). 



Crosse remarks : A small, quite curious species, dull, chalky, 

 with the aperture exactly in the axis of the shell, subtrian- 

 gular, contracted towards the base, and obstructed more or 

 less completely by the presence of a strong parietal tooth. 

 Peristome continuous, strongly reflected and white. 



VIII. AUSTRALIAN SPECIES. 



The Australian Gastrocopts are so closely related to those 

 of eastern Asia that the theory that they were derived from 

 that region appears to have no competitors. Two groups seem 

 to have entered the continent, (1) an ancestral Sinalbinula 

 stock, which probably gave rise also to the exclusively Aus- 

 tralian section Australbinula, and (2) the macdonnelli group 

 of Sinalbinula. In northeastern Queensland, with the islands 

 of Torres Straits and southern New Guinea, the specific uni- 

 formity supports Mr. Medley's view of a Pliocene connection 

 with Papua. 



The inexactness of the existing literature would have stood 

 in the way of any adequate revision of the species had it not 

 been for the generous help of Mr. Charles Hedley of the Aus- 

 tralian Museum, both with information on particular species 

 and with many specimens. I have also the advantage of a set 

 of Central Australian Pupge received from Professor Tate. 

 Several species still require elucidation. 



Key to Australian Species of Gastrocopta. 



NOTE. G. margaretae, no. 97, and G. moretonensis, no. 98, are not in- 

 cluded in the key. 



a. Cohunellar lamella short and wholly horizontal. 



b. Shell sinistral, 2.95 to 3.4 mm. long; New South 

 Wales. G. strangei, no. 94. 



b\ Shell dextral, smaller. 



c. Length 2.6 to 2.9 mm. ; teeth well developed. 



G. pediculus, no. 95. 



