﻿NO. 2 FOSSILS FROM PANAMA AND COSTA RICA — DALL 3 



This species has most resemblance to P. aresta Dall, of Porto Rico, 

 but is more trapezoid in form, with a relatively larger lunule, the 

 hinge teeth are of a different shape, as is also the pallial sinus ; the 

 shell is more nearly equilateral with a shorter, less arcuate posterior 

 dorsal slope. 



CORBULA MACDONALDI, new species 



Shell large, nearly equivalve, having much the outline of Macoma 

 balthica; anterior end longer, rounded ; posterior end shorter ; dorsal 

 margin descending to a small angulation at the end of the basal 

 margin ; from the beak to this angle extends an obscure ridge behind 

 which the surface is less sharply sculptured. There is no analogous 

 anterior radial ridge. Beaks rather low, closely adjacent, the shell- 

 margins evenly apposed with no gape. Surface finely, somewhat 

 irregularly, concentrically striated; right valve with one strong 

 recurved cardinal tooth in front of a pit under the beak which 

 receives the resilium, the anterior and posterior dorsal margins 

 grooved below to receive the margins of the opposite valve. In- 

 terior of the valve smooth, with very distinct muscular and pallial 

 impressions and no pallial sinus ; left valve with a spatulate process 

 divided into a ligamentary and resiliary area by a mesial ridge, and 

 behind it a pit into which the cardinal tooth of the right valve 

 enters ; dorsal margins of the left valve entire. Length of paired 

 valves 19, height 15, max. diameter 10 mm. A larger valve is 23 

 mm. in length and 18 in height. 



Station 5848. Types, U. S. Nat. Mus. 214353. 



This is a very remarkable species not only on account of its un- 

 usual size, but because of its regular form and nearly equal valves. 

 It is named in honor of the collector. 



SPHENIA WALLACEI, new species 



Shell small, myaciform, inequilateral, white; the anterior end 

 shorter, wider, rounded; posterior longer, gradually narrowed and 

 attenuated, terminally roundly truncate; pallial sinus coming nearly 

 to the middle of the shell ; outer surface rude, with irregular con- 

 centric sculpture ; hinge of the usual type in the genus ; length 9, 

 height at beak 5, diameter (left valve only) 2 mm. 



Station 5849. Type, U. S. Nat. Mus. 214354. 



No species, except the very distinct 5\ antillensis of Porto Rico, 

 has been reported from this region. It is named in honor of the 

 former chief engineer of the Canal project. 



