- ] 



varying from lonp-itu.dina] I3? ovate to broadlj? ovate or even suTs- 

 oirci^lar; left valve vrith five to seven strong-, narrow, usiially 

 sharply angular plications, some arisiiig near the umbo anrl hecom- 

 ingr -oroffressively prominent towarci the margin; secondary? plications 

 oe :!asiona] ly int ercalater'i "between the primaries at the margin and 

 iTxtenrling a short distance from the margin; interspaces between 

 the plications deep and sharpl; angitlar; concentric sculpture of 

 laminae, superimposed on the plications and m.ost prominent near 

 the ventral mar-In; right valve almost smooth or bearing plications 

 similar to those on the left; submargins usually corrugated; mus- 

 cle scar, large for the size of the shell, sube^ liptical to s:b- 

 circular in outline, posterior in position; inner margin of the 

 valve at times bearinr minute pustules. 



Dimensions .- lat. 28 mm.; alt. .'?5 ram. 



Remar^'cE .- O. haitensis is represented by only a few small 

 valves. This meager representation is probably not a certain 

 indication of its role in the composition of the- fauna, br.t, since 

 no lar?'e oysters of any species are present, it may be explained 

 by the fortuitous circumstances of collection. It must be rem.era- 

 bere'l, however, that con'^itions maj have been unfavorable for the 

 prolific growth of oysters, since in none of the collections -^o 

 which the writer has had access, are the m.embers of this genus 

 prominent, either in size or in number. The adult Santo Domingian 



