GASTROCOPTA, AUSTRALIA. 169 



The broad, obliquely ascending columellar lamella and the 

 slightly arcuate parietal lamella (in basal view) are features 

 in common with G. hedleyi, but it differs from that by the far 

 smaller lamellae. 



A very similar form has been found in Queensland. See 

 under G. mussoni. Two lots of this species were received from 

 Prof. Tate, evidently, from their appearance, from different 

 localities ; also some specimens mixed with the species he called 

 mooreana, from a third locality, I think. All were labeled 

 "Central Australia"; so that the exact points where the 

 species was collected must remain unrecorded. 



This is a variable species in the number of lamellae and 

 plica? developed in addition to the five constant ones, being 

 comparable to the North American G. pentodon in this re- 

 spect. The forms I have seen may be described as follows : 



(a) Typical larapinta, pi. 30, figs. 5, 6, 7. The parietal 

 lamella is strongly developed, and in basal view is seen to be 

 slightly curved. The lower and much shorter angular lamella 

 converges toward it and is rather weakly connected at the 

 inner end. The infraparietal is tubercular, round or shortly 

 oval, and is present in all specimens seen. In some individuals 

 it is weak and not conspicuous in a front view. This was evi- 

 dently the case with Tate's figured specimen. 



The columellar lamella is large, placed obliquely on the 

 axis, receding upwards, the upper end sloping gradually, the 

 lower and outer end much more abruptly terminated. It is 

 shorter than in G. hedleyi (see pi. 27, fig. 4), but of the same 

 character. 



The basal fold is variable in size, at the junction of colu- 

 mellar and basal margins. The lower palatal plica is rather 

 long and stout. Upper palatal much shorter, subtuberculi- 

 form. Between them an interpalatal plica stands, interme- 

 diate in size between the upper and lower. 



The peristome is thin and well expanded. In some indi- 

 viduals there is a low crest behind the lip, but in others this is 

 scarcely perceptible. 



Length 2.55, diam. above aperture 1.2 mm. 



