52 PROCEEDINGS OF THE ACADEMY OF [1895. 



Genus CERONIA. 

 Ceronia singleyi nov. sp. PI. 3, fig. 3, a. 



Specific characterization, — General form as figured ; beaks promi- 

 nent, turned anteriorly ; anterior side often very elongate ; posterior 

 generally short, obtusely pointed, with an obtuse angle midway of 

 the posterior dorsal margin ; umbonal ridge rounded ; post-umbonal 

 slope of considerable width and nearly at right angles to the face of 

 the valve ; substance of the valve moderately thick. 



The young of this species have a decidedly Schizodesma appear- 

 ance. Older specimens assume the general form of Hemimactra 

 elongata of the Indo-Pacific region. 



This species is known only in the form of casts in a light gray 

 sandstone. It is regarded as a Mactroid shell, and not a Macoma, 

 because (a) the beaks point anteriorly; (b) there is no indication of 

 a twisting posteriorly; (c) the hinge margin of this shell is thick and 

 evidently bore well-developed lateral teeth ; (d) the posterior is very 

 obtuse. 



Locality. — Sunnyside Church, Lee Co., Texas. 



Geological horizon. — Lower Claiborne Eocene. 



Type. — Texas State Museum. 



Genus PERIPLOMA. 

 Periploma collardi nov. sp. PI. 3, fig. 4. 



Specific characterization. — General form as figured ; nearly equi- 

 valve; beaks turned slightly backward; posterior deflected to the 

 right ; substance of the shell thin and very nacreous; umbones fissured. 



The general form of this species is somewhat like that of Ceronia 

 singleyi, from which, however, it is distinguished by the difference 

 in direction of the beaks, as well as by the beaks themselves. Again 

 this species has a much more extended posterior dorsal margin. 



Localities. — Dr. Collard's farm, Sparks' Headright, Brazos Co., 

 Tex. Also mouth of Saline Bayou, Winn Parish, La., and base of 

 bluff at Claiborne, Ala. 



Geological horizon. — Lower Claiborne Eocene. 



Type. — Texas State Museum. 



Genus CORBULA. 

 Corbula aldrichi Meyer, var. smithvillensis nov. var. PI. 3, fig. 5, a. 



The variety is larger than the typical form, beak in the left valve 

 more nearly central; right valve proportionally higher; radiating 

 lines generally obsolete. 



