133 St. Maurice and Ci.aibornk Pki^ecypoda 133 



One instinctively thinks of C /«<^^«z^wz while .looking itpon 

 this specimen, but ?nagnm?i has many more ribs, is more oblique 

 and has less extended, less prosogyrate beaks. 



Type. — Deposited in Paleont. I^ab., C. U. 



Ho7^izon. — St. Maurice Eocene. 



Locality. — Vicinity of Ivong Point, ^ mile below Alabama 

 lyanding, west side of the Ouachita River, lya. 



Protocardia gambrina Gabb, PI. 42. Figs. 2, 3. 



''? P. diversa'" Gabb, Proc. Acad. Nat. Sci. , Phila., 1861, p. 370. 



P. gambrina Gabb, idem, p. 371. 



P. harrisi Dall, at least in part. Trans. Wag., Ill, 1900, p. 1113. 



Regarding this species Gabb remarks : "/*. diversa Con. sp. 

 — A small specimen from Houston Co., Texas, from an Eocene 

 deposit presenting most of the characters of this species, but 

 differs in some few points. It has the form of the typical speci- 

 mens of P. diversa except that the buccal extremity is more reg- 

 ular, the basal margin is entire, and not sinuous as in adult 

 specimens of that species ; this may be however merely the ef- 

 fect of the difference in age. The anterior portion is marked by 

 obsolete cancellations, and the posterior radiations are somewhat 

 different. The ribs are broad and rounded, with small bars 

 placed at short intervals connecting them, while in the young 

 state of P. diversa the ribs are linear with wide spaces and with- 

 out connecting bars. In that species, also, the radiating portion 

 of the surface blends into the adjoining surface by the ribs be- 

 coming obsolete, while in this specimen the same portion ends 

 abruptly, the ribs all being of the same size. It will be necessarj^ 

 to examine more specimens to decide whether this is the young 

 of the above species or distinct. Should it prove so, I suggest 

 the name P. gambrina. ' ' 



Dall remarks regarding this form: "P. gamdrina Gabb, 

 from the Oligocene of Texas, is the young of P. diversa, as Gabb 

 suspected." (Trans. Wag. , III, p. 11 14.) 



Dall seems to have overlooked the fact that this is an Eocene 



