1917.] NATURAL SCIENCES OF PHILADELPHIA. 191 



Area cuneolns n. sp. 



The shell is thin, wedge-shaped, the anterior end short and verv' 

 narrow, the posterior end very wide; beaks small, very convex the 

 convexity narrow; situated at the anteriortwo-fifths, turning somewhat 

 backward. Cardinal area small, not distinctly defined. Sculpture 

 of the convex and posterior parts of the shell of radial flattened, 

 partly bifid ribs alternat ng with narrow riblets, all roughened by 

 transverse granules; the anterior part of the shell having fine riblets 

 and minute concentric threads. Hinge narrow, the tooth-row con- 

 tinuous, of about 27 teeth, a group of very- small ones under the beaks. 



Length 8.8. greatest width 6.25, diam. of left valve 3 mm. 



This peculiar species has a general resemblance in shape to Mac- 

 rodon asperula Dall, Area (CuciiUaria) endemica Dall, and Area 

 culebrensis Smith. It differs widely from them in sculpture. We 

 know of no nearly related species. 

 Area idiodon n. sp. 



The cast is oblong, slightly wider posteriorly, with the beaks very 

 close to the anterior end, full and prominent, and so near together 

 that the beaks of the shell must be closeh' contiguous. Hinge-line, 

 as indicated by a narrow ridge in the cast, is gently arcuate from the 

 posterior end nearly to the beaks. Just below and anterior to the 

 beaks it bends rather deeply downwards and the teeth, as indicated 

 in the cast, are comparatively large. There seems to be about seven 

 of these enlarged teeth in the short, do"WTiwardly-ciirved anterior arc. 

 Inunediately behind this arc there is a space where the teeth seem 

 to have been very small and irregular. The rest of the hinge seems 

 to have had moderately small, regular teeth, indicated by crenula- 

 tions in the cast. The lateral surfaces of the cast has low, irregular 

 concentric waves and numerous ver^' shallow radial impressions. 

 The anterior border is distinctly crenulated, but elsewhere the 

 internal borders of the valves would appear t-o have been smooth. 



Length 69.6, alt. 48, diam. 38 mm. 



Quarry near Wilmington, North Carolina. Type Xo. 12475, 

 A. X. S. P., collected by Mr. Joseph Willcox. 



This peculiar ark differs widely from all Tertiary species knowTi to 

 us. The double curve of the tooth-row, with enlarged teeth on its 

 short anterior arc, is a more specialized structure than we have found 

 in the species compared. The recent A. eampeehensis Dillw. ameri- 

 eana Gray, approaches nearer to A. idiodon than any other known 

 to us. 



Besides the peculiar hinge, this species is notable for its strongly 



