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Bulletin 33 



24 



right valve bears two cardinals of subequal size ; anterior adduct- 

 or impression very large and high with a wide, deep groove be- 

 hind, which would correspond on the shell to a deep adductor 

 scar and ridge between it and the umbonal area ; pedal muscle 

 scar conspicuous and situated dorsal to the adductor, posterior 

 muscle impression and pallial line very indistinct, no sinus notice- 

 able. 



From the dental and muscular structure this form seems to 

 be a descendant of the Pre-Tertiary genus Plearophorus. 



Pleuropopsis unioides, n. sp., PI. 3. Fig. 12. 



Unio sp. Maury, Jour. Acad. Nat. Phila., 2nd ser. vol. XV, 1912, 

 p. 50, pi. VIII, figs. 18, 19. 



Description. — Size and shape as indicated by the figures and 

 explanations ; slight umbonal ridge extends from the beaks and 

 merges into the posterior ventral margin ; surface sculpture con- 

 sists of rather heavy, concentric lines of growth. Longitude of 

 shell 77 mm ; altitude 33 mm. 



Remarks. — This and the following new species from the same 

 locality represent a large collection of casts, the hinge structure 

 of which, for the most part, are but poorly preserved. The 

 fauna is very peculiar and unlike any known. Because of its 

 uniqueness and questionable origin it was thought that the forms 

 should be figured and described as far as possible, thus placing on 

 record the occurrence of such a fauna. 



The species just described, in outline and in the occurrence of 

 the heavy muscular impression, resesembles a Unio. But the 

 presence of clear cut dentition eliminates that genus. We have 

 also in the collection a species of Leda, Nncula and Modiolaria as 

 well as a number of marine gastropoda. 



Type and specimens figured— -Pal. Museum, Cornell Univ. 



Age. — Probably Middle Tertiary. 



Locality. — "One mile west of Godineau River on the shore 

 of the Gulf of Paria, about midway between San Fernando and 

 La Brea, Trinidad." 



Collected by A. C. Veatch in 191 2, then of the General As- 



