Vol. IV] ANDERSON AND MARTIN— NEOCENE RECORD 57 



the center ; umbones full and broad ; lunule indistinct ; hinge 

 line broadly arched; dorsal margins nearly straight in some 

 specimens, slightly rounded in others ; extremities well rounded, 

 the posterior usually more broadly rounded than the anterior; 

 basal margin circular; surface polished, marked by numerous 

 fine concentric lines of growth; two teeth in each valve, the 

 right posterior tooth faintly bifid; muscular impressions inac- 

 cessible. 



Dimensions: — Length of one of the larger specimens, 21 

 mm. ; altitude, 19 mm. ; thickness of single valve, 7 mm. 



Occurrence : — Not uncommon in the middle portion of the 

 lower Miocene of Kern River, California, locality 65. 



This species differs from Diplodonta parilis Conrad and D. 

 harfordi Anderson by its inflated valves, much more prominent 

 umbones, and more elevated beaks. 



Type: — No. Ill, and cot5^pe No. 112, Cal. Acad. Sci., on 

 west bank of a small canyon ly^ miles northeast of Barker's 

 ranch house, Kern County, California. Coll., Bruce Martin. 



Named in honor of Mr. J. P. Buwalda. 



Genus CARDIUM Linn. 



Cardium weaveri, new species 



Plate 1, figures 3a and 3b 



Shell of medium size, rounded at the base, somewhat trigo- 

 nal, inflated ; umbones prominent, curved inward and forward ; 

 anterior dorsal slope short and slightly concave with a cordate 

 area immediately in front of the beaks ; posterior dorsal slope 

 long and slightly convex making a rather sharp curve into the 

 arcuate base ; a conspicuous ridge from the beaks to the pos- 

 terior ventral extremity, giving the valves an angulated appear- 

 ance and forming a prominent posterior dorsal area in each 

 valve; sculpture consisting of numerous equally spaced radial 

 striations which are replaced on the posterior dorsal area by 

 flattened radial ribs separated by narrow interspaces, the radial 

 ribs becoming obsolete near the margin; about twenty radial 

 ribs on the posterior dorsal area, and between fifty-five and 

 sixty fine radial striations on the remainder of the surface; 

 hinge, typical of the genus Cardium. 



