185 St, Maurice and CXaiboune Pelecypoda 185 



CORBULA 



Alabainiensis stock 



The majority of the specimens, seemingly of this stock, in 

 the upper Sabine at Woods Bluff are of the small, strongly con- 

 centrically striate, laterall}^ flattened, compressed form (pi. 56, 

 figs. 1-4, 7) already described in vol. 2 of these Bulletins (p. 

 260, siibeng07iata Dall). These, slightly more specialized in 

 the Claiborne sand, constitute the variety ima of Gregorio. 

 Still, among these are some (figs. 5, 6,8) pointing towards typi- 

 cal alabavihiensis . The latter occur sparingly in rather smallish 

 individuals in the St. Maurice stage from Texas to the Caro- 

 linas. Alongjwith them in this horizon occur specimens, quite 

 inflated, with finer concentric striation, for the most part lack- 

 ing the strong umbonal carination of the species generally, in 

 fact, reminding one of some rather weakly marked Cnspidaria 

 (var. citronella, figs. 12, 13). This type, after becoming a little 

 more rostrate in the Claiborne, appears to be Cossmann's variety 

 Gregorioi (figs. 14-16) though he refers the variety iocompressa, 

 Lea. 



In the Claiborne sand, so called, this stock riots in forms 

 and numbers. Most conspicuous are the large, nasute specimens 

 giving rise to Conrad's name nasuta (figs. 22-26). But others 

 shorten, become thick and elevated, and show in adult forms a 

 noticeable geniculation medially (figs. 26-30). These, var. tecla 

 of Gregorio, are approaching close to the Jacksonian densata ; in 

 fact Dall has it that they really are densata. Typical densata 

 (figs. 31-31J, is a somewhat more elevated form. 



Corbuia alabamiensis Lea, with varieties, PI. 56 



C. alabamiensis Lea, Cont. to Geol. , 1833, p. 45, pi. i, fig. 12. 



C. nasuta Con., Foss. Sh. Tert. Form., 1833, p. 38. See also pi. 19, 



fig. 4 of Harris' Reprint. 

 C. subnasuta d'Orb., Prod., 382. 



C. nasuta Gregorio, Mon. Faun. Eoc. Ala., 1890, p. 231, pis. 36-38. 

 C. alabamiensis Cossmann, Notes Supl., 1893, p. 6. 

 C. alabamiensis Dall, Trans. Wag., Ill, 1898, p. 841. 



For Lea's original description, see these Bulletins, vol. 2, 



