1896.] NATURAL SCIENCES OF PHILADELPHIA. 327 



solved by the material yet studied. C. Bryanti, ruhicundum and 

 Dalli appear to be stages in a continuous or almost continuous 

 series of variations. C. Dalli is the largest form, with the peculiar 

 armature of the aperture most highly developed. €*. ruhicundum is 

 more slender, often much smaller, with the armature less developed 

 in many specimens. C. Bryanti is decidedly smaller, thinner, with 

 the teeth reduced to a mere vestige in the typical form, although 

 specimens occur which seem to establish its intergradation with ruhi- 

 cundum in tooth arrangement. C. Bryanti may be regarded as a 

 stunted race of Diacerion which has re-assumed the characters of the 

 group Maynardia. 



C. Dalli varies from the fine-ribbed typical form with as many as 

 63 riblets on the last whorl, to a rather coarsely sculptured surface, 

 27 ribs on last whorl (40 specimens examined, including one of type 

 lot). 



C. ruhicundxim varies in the same way, Maynard's S. ianthina and 

 S. jmllida being coarse forms. Some examples before me are more 

 elongated and coarse-ribbed than Maynard's types of ianthina, but 

 theintegradation effaces specific lines for these forms. 



There is likewise a very stout variety of C. Bryanti, and as already 

 mentioned, the specimens vary from almost toothless to the typical 

 Maynardia dentition, and onward toward the condition of C. ruhi- 

 cundum. We are indebted to Mr. H. D. Van Nostrand for a large 

 series of these species and varieties. 



66. Cerion Bryanti Pfr.« Malak. Bl. XIV, 1867, p. 130; Novit. Conch., t. 84, f. 14, 

 15. 



Inagua. 



67. Cerion rubicundum Menke.® Catal. Malsb., p. 8 ; Concbyl. Cab., t. 9, f. 8, 9. 



S. ianthina Mayn.* Contr. to Sci., 1889, Vol. 1, p. 69, t. 2, f. 13. 

 S. pallida Mayn* Contr. to Sci., 1889, Vol. I, p. 70, t. 2, f. 14. 



Great Inagua. 



68. Cerion Dalli Mayn.* Contr. to Sci., Vol. 1, 1889, p. 128, 1. 13, f. 23. 

 Great Inagua. 



69. Cerion cylindricum Mayn. Contr. to Sci., 1896, p. 34-36, pi. 7, figs. 3, 4. 

 Great Inagua. We have not seen this form and know nothing of 



its status. 



70. Cerion duplodon P. & V.- PI. XI, fig. 26. 

 Bahamas. 



