170 GASTROCOPTA, AUSTRAUA. 



Length 2.35, diam. above aperture 1.22 nun. (shortest speci- 

 men seen). 



(6) Professor Tate's description was not drawn from any 

 one specimen, but was composite, like the lots he sent out. 

 His figure showing the aperture, copied in my pi. 30, fig. 10, 

 shows angular, parietal and columellar lamellae, basal, upper, 

 lower and interpalatal plicae. This particular form, lacking 

 the infraparietal lamella, is represented by two examples in 

 the series sent me, one of them having the basal fold reduced 

 to a minute vestige. It is relatively scarce, about 12 per cent 

 of the shells received ; and as the terms of the description in- 

 clude also the far commoner form described in paragraph (a), 

 it seems best to regard that as the typical form of the species. 



(c) Similar to the typical form, but the basal fold is re- 

 duced to a small, inconspicuous pad, or not perceptible (pi. 

 30, fig. 11 ; length 2.75, diam. 1.2 mm.) . Often smaller, length 

 2.44 mm. 



(d) Similar to the typical form, but having the basal fold 

 twinned (pi. 30, fig. 9). 



In every specimen of G. larapinta seen, the interpalatal 

 plica is present, with the upper and lower palatals forming a 

 graded series. The infraparietal tubercle is rarely wanting, 

 but the basal plica is decidedly variable in development. 



(e) G. larapinta deserti n. subsp. PI. 30, figs. 1, 2, 3. The 

 shell is subcylindric, thin, gray- whitish. Angular and pari- 

 etal lamellae as in larapinta, but both thinner, the parietal less 

 curved. No infraparietal lamella or tubercle. Columellar 

 lamella and upper and lower palatal plicae as in larapinta. 

 There is no interpalatal plica, and the basal fold is wanting 

 (or in some specimens is present, but small or minute). Peri- 

 stome is well expanded, thin. 



Length 2.25, diam. above aperture 1.15 mm. 



Length 2.25, diam. above aperture 1 mm. 



Central Australia: Tempe Downs, Reedy Creek, Palm 

 Creek, Stuart's Pass, Painta Spring and Alice Springs (Tate, 

 for P. mooreana; Horn Exped.). Northwestern Australia at 

 Forrest Eiver, 18 33' S. lat, 125 8' E. Ion. (Richard Helms). 



