82 BULIMULUS-HYPERAULAX. 



Section HYPERAULAX Pilsbry, 1897. 



Hyperaulax PILS., Proc. Acad. Nat. Sci. Phila., 1897, p. 10 

 (Feb. 23). 



Bulimuli with wave-wrinkled apical sculpture, and an expanded 

 or reflexed peristome, the aperture with a longitudinal groove or 

 channel at the posterior angle and a callous nodule adjacent to it 

 on the parietal wall. Type B. ridleyi. 



Distribution : Fernando Noronha Island ; Miocene of Florida 

 (Silex-beds). 



This group, which is well distinguished by the channel at the 

 posterior angle of the aperture, is apparently extinct, with the 

 exception of a single surviving species. The Floridian Miocene 

 species, B. floridanus Conrad, B. heilprinianus, americanus and 

 stearnsii Dall, are practically identical with B. ridleyi in their main 

 characters, differing only in unimportant details of proportion, size 

 and strration. B. americanus is excessively like B. ridleyi. 



There can be no reasonable doubt that Bulimulus ridleyi is a 

 living representative of the Miocene group, preserved practically 

 unchanged on the remote island of Fernando Noronha, while the 

 group has been wholly crowded out of existence in the continental 

 faunas. 



B. RIDLEYI (E. A. Smith). PI. 14, figs. 11, 12, 13. 



Shell umbilicated, ovate, conic above, moderately solid, brown 

 with a buff line at the periphery, very delicately sculptured with 

 lines of growth, and sometimes low wrinkles and fine impressed 

 spiral strise. Spire conic, the apex obtuse, nepionic whorls sculp- 

 tured with superficial vermicula'te wrinkles. Whorls 5J, slightly 

 convex, the last a little descending and then slightly ascending in 

 front, distinctly constricted behind the peristome ; base perforated 

 by a deep and conspicuous though not wide umbilicus. 



" Aperture ovate, fleshy-brown inside, and showing a pale median 

 line, half the length of the shell ; " peristome flatly reflexed through' 

 out, the outer lip subangularly arcuate above, terminations joined 

 by a thin or thick parietal callus, which is thickened and somewhat 

 tubercular above, separated by a vertical groove or channel from a 

 similar callous lobe on the outer lip near its insertion. 



Alt. 12'5, diam. 7'2 ; alt. of aperture 6'2 mill. 



Alt. 10'5, diam. 6'2 ; alt. of aperture 5'2 mill. 



