CONTRIBUTION TO THE PALEONTOLOGY OF TRINIDAD. 57 



PiUria (Lamelliconcha) labreana 



Figures 



Description. — Shell elongate-ovate, rather compressed, inequilateral, lunule 

 small, well-defined, lanceolate; valve sculptured with narrow, round-edged lamel- 

 lae, with much wider grooves between them; hinge characters shown in the figure* 

 pallial sinus very deep, rounded, broad, extending beyond the center of the valve.' 



Length of shell 17, height 13, diameter 6 mm. 



Remarks.— This species is akin to P. hilli Dall from the Oligocene of Gatun 

 on the Panama canal. It differs from the latter shell in having a bolder, more 

 distally ribbed type of concentric sculpture, and, as far as shown, is much smaller. 



Locality.— Along the shore 1000 feet west of the pier at Brighton, Trinidad, 

 in an impure asphalt. 



Geological horizon.— Upper Oligocene. Equivalent to the Chipolan stage of 

 Florida. 



Genus CALLISTA Poli, 1791. 

 Callista mcgrathiana Rathbun. Plate IX, Figure 10. 



Callista McGrathiana Rathbun, Proc. Boston Soc. Nat. Hist., vol. XVII, p. 255, 1875. 

 Calhsta McGrathiana White, Arch, do Museu Nac. do Rio de Janeiro, vol. VII, pp. 95-96, pi. V. 

 figs. 36, 37, 38, 1887. ' * ' 



Rathbun 7 s original description— " Shell small, elongate, and with the valves 

 moderately convex; length somewhat greater than the height; outline sub- 

 elliptical. 



"The beaks are situated a little in advance of the middle, are prominent and 

 incline rather strongly forward. Their internal moulds are sharply pointed and 

 incurve slightly. The hinge margin descends quite rapidly from the beaks pos- 

 teriorly, and is moderately curved, nearly the same curve being continued in 

 the larger part of the posterior margin, while the ventral margin is also very 

 regularly, but more gradually rounded. 



"The point of greatest convexity of the valves is just above the middle, 

 though the curvature of the surface from the beaks to the ventral margin is usually 

 quite regular. The curvature along the antero-posterior diameter is moderate 

 and more or less regular. The slope toward the posterior and hinge margins is 

 usually quite rapid, and increases in strength near the beaks; it is always well 

 rounded. 



^ "The surface of the shell is marked with numerous small, rounded, concentric 

 raised-lines, separated by similar interspaces of slightly greater width. They are 

 quite equally disposed, sometimes, however, differing in width and placed nearer 

 together. They round up strongly in front. 



"The muscular imprints are of moderate size, slightly excavated, and are 

 situated just above the antero-posterior axis. Of the cardinal teeth, the anterior 

 is nearly perpendicular, bending slightly forward below, while the posterior, 

 which is the longer, extends backward, bending a little downward. The dental 

 prominence in front of the cardinal teeth is somewhat elevated. 



"This small form, not represented by any perfect impression of the exterior, 



