23d New Species of Corbula from Jamaica. 



sponding dimensions of a shell commencing the second stage of 

 growth are .4 inch; .26 inch; .17 inch. 



This species is remarkable for two very distinct stages of 

 growth, with a very abrupt transition from the first to the 

 second. Until a little more than half grown, it is very much 

 like C. Blandiana in the form of the outline, in the sculpture, 

 and in having the valves similarly sculptured, and nearly equal. 

 In the second stage of growth, the larger valve increases nearly 

 three times as much as the other, and the growth is abruptly 

 and strongly directed inwards so as greatly to increase the 

 breadth of an old shell. The sculpture is more irregular, and 

 on the small valve it is much finer, and is covered with a coarse 

 deciduous epidermis. Posteriorly the small valve is deeply set 

 into the larger one. So abrupt is the change from the first to 

 the second stage of growth, that the edge of the umbonial angle 

 in the first makes an angle with the edge in the second of only 

 about 115°, and the general form is made very irregular. It is 

 the analogue of C. speciosa, which inhabits the west coast of tro- 

 pical America. 



Station. — Unknown. 



Hahitat. — Kingston harbor (Jamaica), along " the Palisades," 

 southeast fi^om the city ; A. Barratt ! C. B. A. ! 22 specimens 

 were obtained, of which several were collected by my companion 

 Dr. Barratt, who kindly gave me nearly all his specimens of 

 this remarkable shell. 



CoKBULA SwiFTiANA. C. t. subovoidca, solidissima, inequi- 

 valvi, vix inequilaterali, postic^ acute rostrata; margine ven- 

 trali excurvata : albida : rugis irregularibus et striis concentri- 

 cis; junioribus exilissime radiatim striatis: apicibus parvis, 

 haud involutis: umbonibus perconvexis, antic^ subangulatis, 

 postic^ acute angulatis: dentibus robustis. Long. 10"'.4; alt. 

 5"'.9; lat. 5"'.9. 



Shell subovoid, very solid, inequivalve, slightly inequilateral, 

 acutely rostrated posteriorly, anteriorly well rounded and glo- 



