XXXVI KEY TO UROCOPTID^E. 



2. Axis moderate or of large size, tubular, its cavity vis- 

 ible as a round hole at the truncate summit. 



Ccelocentrum, xv, p. 30. 



II. Smaller forms, the shell 5 mm. or less in diameter, re- 

 taining the spire complete. 



1. Protoconch ribbed; shell long and slender, the axis 

 smooth, with a spiral swelling below the middle in 

 each whorl. Spartocentrum, xv, p. 51. 



2. Protoconch smooth. 



a. Shell thin, slender, the length 4y 2 to 8 times the 

 diam. ; gradually tapering, and attenuate above ; 

 axis with longitudinal white streaks or laminas, some- 

 times interrupted or broken into granules. 



Epirobia, xv, p. 59. 



b. Shell shorter, the length 2i/ 2 to 4 times the diam.; 

 cylindric, with a conic summit. 



Holospira, xv, pp. 66, 300. 



** Axis OP THE SHELL SOLID or barely perforate ; the sum- 

 mit when truncate is closed by a steeply-sloping, flat, or some- 

 what convex septum; aperture higher than wide, the lip not 

 much reflexed, its parietal margin more or less straightened. 

 Shells of medium or large size, all but Archegocoptis Mexican. 



I. Shell gradually tapering to an entire, costulate apex. 



Berendtia, xv, p. 57. 

 II. Shell somewhat cylindric, the summit truncate. 



1. Axis straight or slightly sinuous; shell cylindric or 

 slowly tapering, broadly truncate above. 



a. Surface lusterless, densely sculptured with fine, 

 waved, irregular striae; whorls flattened, the last 

 carinate beneath. Haiti. Archegocoptis, xv, p. 301. 



b. Surface sculptured with arcuate striae, sometimes 

 interrupted by malleation ; base not carinate, though 

 a low cord is sometimes discernible. Mexico and 

 Central America. Oligostylus, xv, p. 8. 



2. Axis encircled throughout with a strong, compressed 

 lamella, median in each whorl. Encalodium, xv, p. 3. 



