1874.] 255 ' [Eathbun. 



of Pernambuco, Brazil. At the former locality it is very abundant, 

 both as interior and exterior moulds. 



Dedicated, at Mr. Derby's request, to Sr. Fredrico Marques de 

 Costa Soares, whose hospitality and efficient aid rendered possible 

 the examination of the localities. 



Family VENERIDiE. 



Callista McGrathiana sp. nov. 



Shell small, elongate, and with the valves moderately convex ; 

 length somewhat greater than the height; outline subelliptical. 



The beaks are situated a little in advance of the middle, are promi- 

 nent and incline rather strongly forward. Their internal moulds are 

 sharply pointed and incurve slightly. The hinge margin descends 

 quite rapidly from the beaks posteriorly, and is moderately curved, 

 nearly the same curve being continued in the larger part of the pos- 

 terior 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 an- 

 tero-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, how- 

 ever, 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, seems to be a true Callista, as indicated by shape and hinge- 

 markings. Size: length, 14 mm.; height, 11 mm.; depth of two 

 valves, 6 mm. 



