Diu^i^oi^ic,.- ' ■.; nl/-.. " ." s-.- --ri.(llyui. . 1. 



> 



J mm. 



-^.emai'ks.- A nuralDer of yr:Ell 'of 



this species, most of them heiia^- la. rger than th , ■"nnt 



s one what v;orn, th^ i- --'.-■<: v..,.: , -^'hese d i u- ' : Itii^th 9.8 

 r:2n., alt., 7 mm.; seniiaiam., C.l mra. The co: ic sculptin-e is 



of the t;y-:pe th^t is well-exeraplif iecT hy 2» s. i and, as in 



that species, un ofibII valves the rlhs are crennlatecT throug-h- 

 out, v;hile on larger ones they are thickened and smooth over 

 most of the aiiterior two-thirds. I^ine to eleven rihs a j.'e present 

 on tho' ■/-- '■ ■." five millimeters of larger shells, hut on small 

 valves this nizmher maj? he increased to fourteen. 



The snail size, long, -almost straight ^octerior ra rgin, 

 P^yc-'■•- --teri^r turning up of fche ventr;iL ::iaigin ' i-ll-defined 

 radials that crenulate the posterior -part of the concentric ribs, 

 are diagnostic feat'^res of 0. retugida. It is -orobahlY a dimJnu- 

 tive offshoot ox the stock v/aich produced gup";:i , from the young 

 valves of which it differs hy being more elongated, with a long- 

 er and straighter posterior dorsal margin .: ire distinct rad- 

 ials. 



O ccurrence .- lov/er Miocene : Bowden beds, Bov/den, Jam.aica. 



