188 PROCEEDINGS OF THE ACADEMY OF [April, 



Length 32, alt. 19, diam. of left valve 9 mm. (type). 

 " 33.5, " 20, " '' " " 11.25 " 



Type No. 2859, A. N. S. P. 



Besides a number of valves agreeing with the above description, 

 there are two entirely similar except that they have 32 ribs. 

 Area (Scapharca) proletaria n. sp. 



Shell oblong-trapezoidal, wider posteriorly, inflated, with rather 

 large umbones, beaks at the anterior fourth. Cardinal area very 

 narrow^ and bounded by a narrow ridge posterior of the beaks, wider 

 and triangular in front of them. Ends of the hinge line angular. 

 Anterior end rounded, posterior oblique. Sculpture of 35 ribs 

 about equal to the furrows, in the left valve closely granose except 

 on the posterior slope; interstices sharply but irregularly striate 

 transversely. Right valve with some of the anterior ribs partly 

 granose. Hinge with a continuous row of 15 + 31 teeth. Margin 

 fluted. 



Length of left valve 30, alt. 21, diam. 10 mm. 



Type No. 2965, A. N. S. P. 



There are 4 right and 4 left valves of this species, not paired. It 

 is a decidedly broader shell than the preceding species but otherwise 

 related. 

 Area dolaticosta n. sp. 



The shell is extremely plump, almost equilateral, and equivalve. 

 The ends of the hinge are slightly produced ; posterior margin some- 

 what straightened, anterior and basal margins rounded. Beaks 

 very prominent and full. Cardinal area broad (almost wholly 

 concealed by hard shale). Sculpture of 25 high ribs bearing rather 

 large, irregular nodes lengthened in the direction of the ribs. It is 

 similar in right and left valves. 



Length 65, alt. 63, diam. 66 mm. 



Type No. 2738, A. N. S. P., from the shale of Chiriqui collected 

 by Dr. John Evans. 



Two specimens of this very distinct ark were found with the lot 

 of A. chiriquiensis. The shape and sculpture are characteristic. 



The shale bed at Chiriqui may perhaps be equivalent to the lower 

 or lignitic bed at Tower N on the Canal and therefore Oligocene. 



Area chiriquiensis, Gabb, is probably A. patrica, Sowb. A. grandis 

 also occurs in Santo Domingo. 

 Area (Scapharca) eoccopleura n. sp. 



A small, very obese nearly equivalve species with the postbasal 

 angle somewhat produced, a rounded angle running to it, the beaks 



