1866.] GUPPY WEST-INDIAN TERTIARIES. 581 



Lower Miocene, Manzanilla, Trinidad ; Upper Miocene, Jamaica. 

 It also occurs in the Pliocene of Trinidad. 



7. Cercomya led^formis, spec. nov. 



Shell transverse, elongate, inequilateral, thin, closely covered with 

 numerous fine and regular longitudinal or concentric ridges ; ante- 

 riorly rounded; posteriorly produced into a pointed rostrum, of 

 which the upper margin is concave ; posterior cardinal area strongly 

 impressed. 



In addition to the strong ridge defining the cardinal area a second 

 ridge runs from the umbo to the end of the rostrum, upon which, in 

 some examples, the concentric ridges rise into small points. 



I have not been able to observe the details of the hinge of this 

 shell. The right valve alone has occurred to me in a moderately 

 perfect state ; but fortunately I have discovered some shattered left 

 valves, which prove that this shell is not a Pandora with a flat left 

 valve, which I at first imagined it might be. I have therefore con- 

 sidered it to belong to the genus Cercomya, which has not hitherto 

 been recorded from Tertiary rocks. 



Lower Miocene, Manzanilla, Trinidad. 



8. Mactrinula macescens, spec. nov. 



SheU oblong- sub trigonal, thin, compressed, nearly equilateral, with 

 broad transverse sulcations, which begin at the keel-like ridge on 

 the posterior margin, and are continued to the rounded and somewhat 

 produced anterior margin; umbones small, depressed; posterior 

 marginal area separated by an acute keel, extending from the umbo 

 to the angle of the inferior margin ; hinge with a double cartilage- 

 pit and a /\ -shaped cardinal tooth in the left valve ; laterals in the 

 same valve lameUar, forming a deep groove for the ligament ; laterals 

 in the right valve lamellar, doubled ; cardinal tooth obsolete. 



The nearest recent ally of this shell is M. plicataria, Linn., which 

 is an inhabitant of the Indian Ocean. It is more distantly related 

 to M. prcBtenuis, Conrad, of the Eocene deposits of North America. 



Lower Miocene, Manzanilla, Trinidad. 



9. Venus Walli, spec. nov. 



Shell subtrigonal, somewhat inequilateral, anteriorly rounded, 

 posteriorly somewhat angular, ornamented with numerous small and 

 fine close radiating costellse, interrupted by high concentric crenu- 

 late ridges, which are higher and closer towards the ventral margin ; 

 umbones small, prominent ; lunule impressed, sinuately striated, 

 circumscribed by a sharp groove ; posterior cardinal area distinct, 

 striate. 



On the disk the costellae are distinctly paired, with a smaller 

 intermediate costella between each pair ; but near the keel which 

 runs from the umbo to the posterior angle, separating the striate 

 posterior margin, the costellae are larger and single, and the concen- 

 tric ridges die away into the striations. 



This species is related to the recent V. cancellata. 



Lower Miocene, Manzanilla, Trinidad. 



