107 - 



tvi'o groups, one of five and the other of two, hy a posterior broad 

 depression and, si. ce the shell is heavy, the plications soaroely 

 affect the margins; besides, the marsin r^f the left Vr^.lve is strong- 

 ly upturned and the right vf;lve correspondingly reflexed. The 

 small, thin, elegantly sculptured 3o';;den forms are scarcely com- 

 parable 7.1th this passive species, but the typical large haiten -^ 

 sis approaches it more closely. Brovm states that "at '.Tilloughly 

 Bay [Antigua] a much larp-er species of oyster was observed, ;oer- 

 haps 0. haitensis Sowerby." (l) 0. rtif^ifera Sail {?.) from the 



(1). idem, TO. 6^:^. 



(2). loe. cit. , p. 687, 1898, (as 0. sellaeform.is Oonrad, var. 

 rne-ifera. 



Tampa silez and Ghipola horiR;ons never attains the size of haiten- 

 sis and may be distinguished from the yomi^ of haitensis by the 

 coarser ribbing in the right valve and the more exfoliate" 1am-.- 

 ellae in the left. The Oak Grove 0. pauciplicata Dall (S) has a 



(?), idem, (as 0. sellaeformis Ooiirad, var. pauciplicata . 



more falcate outline and more regular concentric lamellae. vThen 

 C^abb described the California faimas he v/as not acquainted .':s he 



