- 402 - 



Tyy>e locality .- '^OT/clen, "^amaica. 



Shell srrall, nioderatelj' Inflated, slightly inequilateral, 

 suborhicular, the anterior end heing more convex than the poster- 

 ior and curvijng more hroaolj- into the base; innhones lov/, moderate- 

 ly inflated; esrternal sculpture consisting of thirty-nine to forty- 

 two low, suhrounded radial ribs separated by interspaces of the 

 same width or slightly narrower, the interspB'''--:"^ visually crossed by 

 ver-; fine concentric striae; ribs ornamented with a single row or 

 more or less globiilar or slightly transversely swollen nodules; 

 on the anterior eight or nine ribs the nodiiles largest and occupy- 

 ing the entire ' ' " of the ribs; the nest seven ribs having the 

 nodules progressively shifted to the anterior side; of the succeed- 

 ing fourteen ribs on the first fev; the ■-^'■tit"'.c cr-c-^j^ occiropying the 

 entire width of the rib and ventrally more compressed transversely 

 while on the remainder the nodules gradually shifted to the post- 

 erior side and the interspaces between the ribs becoming slis-htly 

 deeper; the ten posterior ribs characterized by a narrow anterior 

 keel and a lov/er, broader posterior portion on which the nodules 

 are situate ''-, the interspaces t-^ t-^^n +:he posterior ribs relatively 

 v/ide and shallow; posterior margin of the valves deeply serra.te. 



Dimensions ,- Lat . , 19.5 mm.; alt., 19,3 ram.; semidiam., 

 7 rr-jn. 



?.emarl:s .- Several valves of this species are ■oresent. The 

 one measured is much larp-er than any of the others. The ribs on the 



