﻿8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 59 



as wide as the lumen of the whorl. As it recedes toward the apex of 

 the spire it becomes narrower and also ascends more rapidly than the 

 coil of the whorl, so that when it has completed one turn it appears 

 midway between the roof and base of the whorl and is also much re- 

 duced in width ; at the completion of the second turn it is close to the 

 roof of the whorl and exhibits a short, broad subtriangular horizontal 

 expansion ; in the next turn it has become again a simple thread-like, 

 low plica which is at the junction of the roof of the whorl and the 

 axial wall, and so continues up the spire. 



PHENACOTAXUS INFUNDIBULUM Pfeiffer 



Bulimus infundibulum Pfr., Proc. Zool. Soc. Lond. for 185 1, p. 255. 

 Bulimulus (Ataxus) infundibulum Pilsbry, Man. Conch. 10, p. 131, pi. 44, f. 

 89-92, Mar. 1896. 



Right bank of the Rio Pampas, on road from Bombon to Pajonal, 

 Peru. Dr. H. Bingham. 1 U. S. N. Mus., No. 209266. Province of 

 Ayachuco, Peru, Pfeiffer. 



In this species the internal lamella begins abruptly in the inner half 

 of the last whorl as a strong, stout plate with a much thickened 

 distal edge which nearly reaches the opposite (outer) wall of the 

 whorl, and has its margin recurved toward the base of the whorl. 

 The part joining the pillar wall is thin, and (in the specimen ex- 

 amined) has a rather large perforation. The plate curves round the 

 inner wall of the whorl, ascending in one turn from the middle of 

 that wall nearly to the angle of that wall with the roof of the next 

 whorl, and at the same time diminishes in size and strength to a 

 low, sharp, simple lamella. This is traceable as a mere thread in the 

 two preceding whorls. 



PHENACOTAXUS UMBILICATELLUS Pilsbry 



Bulimulus (Bostryx, Ataxus) infundibulum var. umbilicatellus Pilsbry, Man. 



Conch., vol. 10, p. 131, pi. 44, f. 93, 94, March 1896. 

 Bulimulus (Bostryx) umbilicatellus Dall, Proc. U. S. N. Mus., vol. 38, No. 



1736, p. 179, June 1910. 



Rio Pampas, with the last species, Dr. Bingham. U. S. N. Mus., 

 No. 161618. 



Externally this species differs chiefly from A. infundibulum by 

 being more slender, so that Dr. Pilsbry regarded it as only a variety 

 of the latter ; and this opinion was justified by the appearance of the 



1 These specimens were obtained by Dr. Bingham on a previous journey, the 

 mollusks of which are described in the Proceedings of the U. S. Nat. Museum, 

 number 1736, pp. 177-182, June, 1910. 



