UROCOPTIS, S. G. GONGYLOSTOMA. 213 



6. 10 x 2.75 mm., with 10 whorls. 



U. difficultosa, no. 96. 



c. Larger, 13-21x3.5-4.5 mm., whorls 9-12. 



U. I. trinidadensis, no. 97. 



d. Larger, 17.5 x 4 mm., whorls 13 ; whitish, 

 base carinate. U. prima, no. 92. 



2. Striae rather fine, subobsolete on the convexity of 

 each whorl; axis slender, the upper lamella small, 

 not extending into the last two whorls. 



U. cristallina, no. 100. 



3. Densely striate, 16x4 mm., with 13 whorls ; upper 

 lamella stronger. U. confusa, no. 93. 



4. Very densely, sharply and finely striate, 13 x 3.2 

 mm. with 12, to 16.5 x 3.4 mm. with 14^ whorls ; 

 axis stout, with two strong lamellae. 



U. fortis, no. 95. 



5. Very finely, subeffaced striate, glossy, the whorls 

 nearly flat; 12-15.5 mm. long, 2.7-3 diarn., whorls 

 10-13 ; upper axial lam. stout, rounded, the lower 

 compressed, less wide. U. planospira, no. 94. 



6. Smooth, the last whorl striate ; suture crenulate ; 

 21 x 4 mm., 12 whorls ; interior unknown. 



U. lavalleana, no. 97. 



7. Finely striate, the lower axial lamella slightly 

 more widely projecting than the upper. 



U. hilleiana, no. 91 ; U. e. subelegans, no. 90 b. 



8. Finely striate, the upper axial lamella slightly 

 predominating over the lower, a median one often 

 developed. 



a. Cylindric, with 10%-16 whorls. 



U. elegans, no. 90; U. arangiana, no. 89. 

 6. Fusiform, 10-12 whorls. 



U. e. aubcriana, no. 90 a. 



III. Small, striate or with spaced riblets, two weak lamellae 

 encircling the axis (group of U. angustior). 

 1. Shell truncate when mature. 



a. Sculptured with strong, narrow riblets; 121/2 

 x 3 mm., whorls 12. U. fusiformis, no. 104. 



