128 PTERODISCUS. 



solid. Spire depressed, very widely conic, rather obtuse. 

 Whorls 5, regularly increasing, a little convex, the suture 

 impressed, last whorl carinate, convexly sloping above, con- 

 vex beneath, slowly but not deeply descending for a long 

 distance in front. Aperture oblique, armed with an acute 

 revolving simple columellar lamella, emarginate, irregularly 

 circular, angular outwardly, the base rounded, margins re- 

 mote, columellar margin straightly sloping, forming an angle 

 with -the basal margin. Greater diam. 10, lesser 9, alt, 6, alt. 

 of aperture 3.5 mm." (Ancey) . 



Oahu: Waianae (Baldwin). 



Amastra heliciformis ANCEY, Bull. Soc. Malac. France, vii, 

 1890, p. 340. THWING, Occas. Pap. B. P. B. Mus., iii, no. 1, 

 p. 162, pi. 3, f. 17 (?). 



"This Amastra is quite lens-shaped and Heliciform, but it 

 is 'to be grouped as an extreme form, allied to A. kaiiaiensis, 

 agglutinans and sphccrica" (Ancey) . 



Not seen by Pilsbry, but Hyatt prepared the following 

 noles from specimens submitted by Mr. D. D. Baldwin : 



This extraordinary helix-like form has a large open um- 

 bilicus and depressed spire, with a strong angulated border 

 to the umbilicus and coarse but regular striae of growth ; the 

 spire even in the extreme young has a very wide angle. The 

 subangulation of the whorl is broad or truncated or with an- 

 gulated edges, and may have longitudinal ridges both on its 

 flattened ridge and accompanying it on the sides. This ap- 

 pears late in life of the shell and persists, as in Amastra cy- 

 clostoma, throughout life, to a late stage. The spire is more 

 elevated and more carinated than in the shells collected by 

 Mr. Cooke and described as Pterodiscus cookci. The calcar- 

 eous layer, in the three shells received from Mr. Baldwin, is 

 deficient in large part, so that it is difficult to handle them. 

 The form, columella, the plication or tooth, and the young, 

 show that this is an ally of Amastra spherica. Mr. Baldwin 

 kindly states in a letter that, the shells so far collected by him 

 are free from agglutinations. 



