152 MACROCERAMUS, CUBA. 



14, fig. 10), or with " three short, blunt cusps, the middle 

 the largest, all three with distinct cutting points " (pi. 14, 

 fig. 5, M. gossei of Jamaica, after W. G. Binney). The side 

 teeth are all of one form, having a long, rather narrow inner 

 cusp or mesocone, and a very small ectocone. The very in- 

 distinct basal-plates seem to be oblique to the cusps in M. 

 pontificus. Binney figures them as long and straight in M. 

 gossei (fig. 5). The outer teeth are a little shorter and wider 

 (fig. 9). The formula is about 40.1.40 in M. gossei of 

 Jamaica (Binney) ; 35.1.35 in M. pontificus. M. turricula 

 has teeth much like those of gossei, according to Binney 

 (Ann. N. Y. Acad. Sei., iii, 126). 



Distribution : Greater Antilles, chiefly in western Cuba ; 

 Curacao; mainland from Central America to Texas; south- 

 ern Florida and Bahamas; usually living under stones (lime- 

 stone), coming forth in wet weather. 



The species now segregated in the genus Microceramus 

 have hitherto been placed in Macroceramus, owing to the 

 general similarity of the shells. We owe to Binney and 

 Bland (1872) the first intimation that Macroceramus was a 

 composite group. They found that M. gossei has a type of 

 dentition different from M. signatus; but their observation 

 was not utilized in taxonomy, nor was its significance from 

 an evolutionary point of view appreciated. In 1898 the sub- 

 generic name Microceramus was given to the smaller, thin 

 species of Macroceramus, but without knowledge of the im- 

 portant characters of the group. That name, however, being 

 based upon a member of the gossei group of forms, will now 

 take generic rank. 



Microceramus differs from all TJrocoptince in the straight, 

 not v-shaped, rows of teeth of the radula, and in the form of 

 the individual teeth, the inner cusps of which arise near 

 the anterior border of the basal-plate, adjacent to the outer 

 cusp, instead of being carried backward on the basal-plate 

 as in all Urocoptince. Moreover, the cusps are pointed, 

 not blunt and rounded. It agrees with the Urocoptince in the 

 fragile, high-arched, plaited jaw, with a triangular median 

 section ; in the narrow median tooth of the radula ; and in 



