St. Maurice and Claiborne Pelecypoda 



would not have made had he ever seen Lea's shell. Occasionally 

 at Claiborne and especailly at Gosport this species shows speci- 

 mens of six or more inches in length (pi. i). Some, of this 

 character, in the Philadelphia Acad. Coll., are labelled in Con- 

 rad's handwriting Ostrea daibomensis. 



We strongly suspect that the surrounding conditions at 

 Claiborne during the deposition of the "sands" M^ere not favor- 

 able for 03'Ster development. Shells grown to considerable size 

 are often thin, very gibbous and AnomiaASk.^ (pi. 2, fig. i and 

 pi. 6, fig. i). These specimens show the exterior radiating lines 

 already referred to at great advantage. If the 03^ster lives be- 

 yond this stage, it seems diseased and is usually verj^ much de- 

 formed in some way or other (pi. 2, fig. 3). Parts ma}' be very 

 thin or thick ; exteriorh" smooth or highly foliated (var. frionis 

 pi. 5, fig. I ; marginal crenulations may be present or absent ; 

 a great lengthening of the shell is of common occurrence, 

 causing a contracted appearance toward the beak. Hence the 

 derivation of the variety contrada {Vroc. Ac. Nat. Sci. Phila., 

 1855, p. 269 ; and Mex. B'd^^ Surv., p. 160, pi. 19, figs, i, a b c 

 d, 1857) of the Rio Grande section. Not all the specimens along 

 the river are "contracted." The more southerly, Jackson ex- 

 posures as a rule furnish the t3-pical contrada while the northerly 

 exposures, furnish more nearly tj'pical alabamiensis. In this sec- 

 tion of the country in late Eocene times, it appears that condi- 

 tions were less hostile to this tA^pe than at Claiborne. Far to the 

 east again, in eastern Georgia, South Carolina and North Caro- 

 lina the georgiana flourished in great profusion. That this is the 

 eastern equivalent of contrada or well-fed alabamiensis , we have 

 no doubt. It often shows the peculiar, radiate marking of the 

 exterior referred to above. 



Type. — Alabamiensis. No. 5439 Phila. Acad. Of contrada, 

 U. S. Nat. Mus. 



Horizon.-^^t. Maurice, Claiborne and Jackson Eocene. 



Spedmens figicred. — Mostlj^ Mus. Cornell Univ. ; but pi. 4 

 and pi. 5, figs. I and 3 from Texas State Mus. 



Localities. — Texas : Along the Rio Grande 2 mis above San 

 Jose, just above the mouth of Good Cr. , Zapata Co. ; at Webb-Za- 



