i8o Bulletin 31 180 



Periploma claibornensis Lea, PI. 55, Fig. i 



Anatiua claibornensis Lea, Coat, to Geol. , 1833, p, 40, pL i, fig. 8, 



Lea's original description. — A portion of the hinge only of this 

 shell has come under my notice, consisting of the apophysis, the point of 

 the beak, and a small part of the dorsal margin behind the beak. The 

 apophysis is elliptical, and small comparatively with the thickness of the 

 valve in the region. The figure is a good representation of the part de- 

 scribed, and it will be observed that the substance of the shell is much 

 thicker than anj"^ described species. The pearly nacre which distinguishes 

 most of the genus is very observable in this. 



We have two specimens like Lea's but showing nothing fur- 

 ther in regard to the nature of this species or its relationship to 

 the various forms from the St. Maurice beds below. The type 

 of No. 5023 is still in the Academy's collection, Philadelphia, Pa- 



Periploma collardi Harris, PI. 55, Figs. 2-5 



7\ collardi Har. , Proc. Phila. Acad. Nat. Sci., 1895, p. 52, pi. 3, fig.4. 

 P. collardi Dall, Trans. Wag., Ill, 1903, p. 1528. 



Harris' original characterization . — General form as figured ; nearly 

 equivalve ; 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. 



The tj'pe specimen was from Dr. Collard's farm, Sparks 

 Headright, Brazos Co., Texas. It is more elongate than the 

 specimens from the base of the bluff at Claiborne from the same 

 horizon. Those from St. Maurice, lya., show an intermediate 

 outline usually, though the elongate, Texan form occurs. Some 

 at the base of the Claiborne bluff after • having been probably 

 distorted by pressure assume a nearly circular outline and are 

 considerably inflated. But what seems to be the prevalent form 

 here is shown by fig. 3. Fig. 5 shows very beautiful radiate 

 structure to good advantage. All these specimens are thin 

 shelled and highly nacreous. 



In the Orangeburg District, S. C, a variety or distinct spe- 

 cies is much thicker, nearly circular, flat and Z7^«wa-like in as- 



