158 KANSAS UNIVERSITY SCIENCE BULLETIN. 



in a manner approaching some of the Mesozoic members of 

 the family. Length, 12 mm. ; height, 8 mm. ; beak, 5.5 

 mm. from front. 



Whitehorse spring, Oklahoma; very rare. 



This may not be a Schizodus, but the hinge is so poorly 

 preserved that none of its characters are shown. It seems to 

 resemble Schizodus as much as anything else, and is provision- 

 ally referred to it. 



AVICULOPECTEN OKLAHOMAENSIS, n. sp. 



Plate V, figares 3-3c; plate VI, figures 11-IIc. 



Shell like A. occidentalis in most of its features, and may 

 be but a variety of it. The hinge is nearly equal to the 

 length of the shell. The beak projects above the hinge, is 

 acute, and in many spcimens is inflated, erect, or slightly in- 

 clined forward. Anterior ear well defined, convex, rounded 

 at the extremity, separated from the umbo by an angular 

 depression and is marked by about nine coarse radiating 

 striae or costse and covered with close-vaulted scales. Little 

 can be made out of the posterior ear of the left valve, except 

 its general form, which is quite angular. It is separated 

 from the shell by a rounded furrow. The posterior ear ap- 

 pears to be about as long as the anterior, and nearly smooth 

 except for concentric lamellar markings. The surface is 

 marked by two- or three-ranked costse, according to their age, 

 the later ones being smaller and implanted between the 

 larger ones. They are straight or somewhat flexuous, flat- 

 tened, and separated by furrows of about their own width. 

 These are crossed by rather coarse lamellae which may be 

 rather distant or crowded, depending on the rate of growth 

 of the individual at any point. These lamellae are coarser 

 than those of A. occidentalis. Right valve, probably belong- 

 ing to this species, nearly flat, beak not elevated, outline and 

 ears much as in the left valve, except the anterior ear, which 

 is deeply cut by the byssal notch. Both ears show faint ra- 

 diating costae and concentric marks. Body of the valve 

 nearly smooth, with but trace of radiating costae. 



Whitehorse spring, Oklahoma ; abundant. Dozier, Tex.; 

 rare to common. 



