32 COELOCENTRUM. 



obliquely vertical lamellae. Nepionic whorls un- 

 known. Coslocentrum s. str. 

 2. Internal axis without vertical sculpture. 



a. Internal axis cylindric or swollen within each 

 whorl, smooth. Exterior of the shell with more 

 or less spiral sculpture developed. Nearly 7 

 nepionic whorls, the first dome-like, the rest 

 cylindric, obsoletely costulate, especially near 

 the sutures. Liocentrum, p. 46. 



b. Internal axis sub-cylindric, within the last and 

 penultimate whorls encircled close to the base 

 by a spiral lamella. Nepionic shell unknown. 



Elasmocentrum, p. 49. 

 II. Slender species, retaining all of the whorls in maturity. 



c. Internal axis hollow but slender, smooth, swol- 

 len within each whorl. Whorls many (16-22), 

 higher and less crowded than in other sub- 

 genera. Nepionic shell of about 5 whorls, the 

 apex bulbous, first 2y 2 whorls vertically 

 straightly costellate, next 2 whorls decussated, 

 granulose. Spartocentrum, p. 50. 



Section COELOCENTRUM s. str. 



In this group the internal pillar is swollen below the middle 

 within each whorl, excavated below this spiral ridge, and 

 sculptured with obliquely longitudinal riblets or lamellae, 

 which vary from smooth to serrate at the free edges, and are 

 often irregularly interrupted, some of them replaced by gran- 

 ules scattered on the polished surface of the tube. The rib- 

 lets do not extend into the excavation below the ridge, and in 

 one species, C. astrophorea, there is a spine on each where it 

 crosses the spiral ridge. 



The species are rather numerous and not often separated 

 by strongly marked characters. The following key is there- 

 fore of no great value. The number of preserved whorls is 

 quite variable individually, and is not even constant in shells 

 of the same dimensions. 



