582 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 20, 



10. Ctthekea juncea, spec. nov. 



Shell subtrigonal, rounded anteriorly, and somewhat angular and 

 truncate behind, ornamented with numerous thin concentric lamellae, 

 alternately rather higher; posterior cardinal area slightly folded, 

 rather indistinct ; lunule impressed, striated ; umbo small, incurved ; 

 hinge-teeth strong, the hinder (of the right valve) bifid, the two 

 anterior ones compressed, close together, and having before them a 

 deep oblong pit for the reception of the tooth of the opposite valve. 

 Hinge- area with a long groove extending from the termination of 

 the ligament nearly to the posterior angle. 



Upper Miocene, Cumana. 



11. DosiNiA cYCLicA, spec. nov. 



Shell nearly orbicular, thick, subin equilateral, scarcely swollen, 

 finely and regularly concentrically striated, with occasional deeper 

 subrugose lines of growth towards the ventral margin; umbones 

 small, compressed, and closely approximate ; lunule entirely wanting ; 

 margins plain. Hinge consisting of a broad flat plate circumscribed 

 by the raised dorsal margin ; teeth three, large ; the central and 

 largest one placed immediately under the umbo ; the other two 

 lamellar and divergent, the posterior one largest. 



This shell has the general shape of Dosinia discus. It is also 

 allied to D. orbicularis of the Bordeaux deposits. It wants the 

 lunule and the small anterior tooth ascribed to the genus Dosinia, 

 and I thought at first of referring it to Cyclina. The general 

 character of the hinge, as well as of the exterior, however, resembles 

 that of D. orbicularis so closely that I have decided to place it under 

 the same generic name as that species. It is evidently intermediate 

 in some respects to the two genera mentioned. It is readily distin- 

 guished from D. acetabulum, another species to which it bears some 

 resemblance, by the very different arrangement of the hinge-teeth, 

 by the total absence of a lunule, and by the umbo being less in- 

 curved. 



Lower Miocene, Manzanilla, Trinidad. 



12. Caedifm castum, spec. nov. 



Shell subovate, somewhat oblique, ventricose, ornamented with 

 about twenty-two stout, rounded, radiating ribs, imbricated by 

 numerous transverse striee, which are continuous across the inter- 

 stices ; umbones small, prominent ; posterior margin divided from the 

 disk by a rounded carination ; margins pectinate. 



Allied to the recent C. obovale, Sow. In young examples the 

 difference in size of the ribs on the disk and those on the posterior 

 margin is more marked, and gives a strongly carinate appearance to 

 the sheU, which is scarcely so conspicuous in larger specimens. 



Lower Miocene, Manzanilla, Trinidad. 



13. Erycina tensa, spec. nov. 



Shell ovate, subequilateral, minutely striated concentrically with 

 about fourteen low and somewhat distant radiating ribs ; anteriorly 

 rounded, posteriorly truncate ; umbones not prominent. 



