20 ANNALS NEW YORK ACADEMY OF SCIENCES 



C. adansoni. In other words, the primary spirals are not so highly de- 

 veloped, and spirals of higher order are coarser. This difference persists 

 throughout the remainder of the shell growth. On the sixth volution, 

 beyond the protoconch, the upper of the two primary spirals becomes 

 more prominent. This tendency increases until, on the body volution, 

 the ribs have become contracted into spines, of which the upper primary 

 spiral forms the most projecting portion. The spirals of higher order 

 increase rapidly in number until they become so crowded that they 

 coalesce, forming broad, flattened ridges which are in places finely striated, 

 indicating the original spirals of which they are composed. On the body 

 whorl the uppermost spiral breaks up into fine nodes, and just before the 

 end of this volution three spirals on the shoulder become similarly no- 

 dose. On the lower slope of the volution there are also three strong 

 spirals which become nodose toward the end of the whorl. Spines are 

 absent from the under side of the body volution, as in C. adansoni. 



The aperture is broadly oval. The inner lip bears a strong callus, 

 with a well-developed tooth forming, with the outer lip, a short canal at 

 the posterior portion of the aperture. The anterior canal is short and 

 slightly curved. The outer lip is flaring, its margin being crenulated by 

 the spirals of the outer surface. The lower margin of the outer lip 

 grows more rapidly than the upper, forming a projection somewhat as in 

 Cerithium tuberosum, but not so strongly developed as in the latter 

 species. There is considerable difference in the degree to which this 

 feature is developed on several individuals of C. echinatum. 



Horizon and locality : Recent. Zanzibar. 

 No. 40181, Columbia University collection. 



Eemarks : This shell bears a strong resemblance to C. adansoni, but 

 differs in the coalescence of the fine spirals, which on C. adansoni remain 

 distinct throughout the life of the shell, covering all the coarser features 

 with fine thread-like lines. On C. echinatum also nodes are developed 

 to a less degree, appearing only on the latest portion of the body volution. 

 The more rapid growth of the lower portion of the outer lip on C. echina- 

 tum is an important distinguishing feature, since it does not occur on 

 C. adansoni. 



C. echinatum. as shown by its early development, is closely related to 

 C. tuherosum, but it is a more accelerated shell, since it loses the vertical 

 element from its outline on the sixth volution, instead of the tenth, 

 as in C. tuberosum. "While more accelerated than C. tuberosum . it is 

 more retarded than C. adansoni, since it does not acquire nodes until 

 near the end of its life historv. 



