192 CCELOCION. 



line of plicate-mouthed ancestors stretching back into Meso- 

 zoic time. The senile feature of an uncoiling last whorl 

 seems to point to Ccelocion as the last of its ancient race. 



3. P. AUSTRALIS (Forbes). PL 29, figs. 18, 19; pi. 30, figs. 

 25-29. 



Shell umbilicate, cylindric, slowly tapering to the rather 

 broadly truncate summit; white under a thin greenish-yellow 

 cuticle, which is almost entirely lost in adult individuals; 

 moderately solid. Surface but slightly shining or lusterless, 

 sculptured with thread-like longitudinal riblets, much nar- 

 rower than their intervals. Whorls numerous, somewhat 

 convex, the last noticeably angular at the periphery, pinched 

 into a cord-like keel around the narrow, somewhat funnel- 

 shaped umbilicus; the last whorl becoming shortly free from 

 the preceding in front. Aperture subvertical, pear-shaped, 

 distinctly narrowed above, subangular below, where it is chan- 

 nelled within. Peristome free, a little expanded, the parietal 

 margin with a prominence in the middle, marking the end 

 of a low ridge or lamella running inward. Axis rather large 

 and tubular, encircled by a small spiral cord near the base. 

 In the penult, whorl this cord widens into a flat lamella, and 

 is accompanied by another similar lamella above it on the 

 pillar ; both decreasing and extending downward into the first 

 half of the last whorl. There is also a plica on the outer wall 

 near the lower partition in the penult, and first half of the 

 last whorl (pi. 30, figs. 28, 29, pal.), and a lamella on the 

 parietal wall, beginning within the back of the last whorl, 

 and penetrating about one whorl inward. 



Length 22, diam. above aperture 4.5 mm.; whorls 11%. 

 N. Pine River. 



Length 20, diam. above aperture 4.3 mm.; whorls lOi/2- 

 N. Pine River. 



Length 18, diam. 4, aperture 4 mm. long; whorls 11. 

 Forbes 7 type. 



Length 18, diam. above aperture 4 mm. ; whorls 9. Warroo. 



Length 18.5, diam. above aperture 4 mm.; whorls 11. 

 Warroo. 



