7^ Bulletin 31 78 



Where there are great numbers of very j^ouiig of planicosta 

 and small rotunda, as in the Claiborne "sand", it is something of 

 a task to separate the two, for each show a nearly circular out- 

 line and have crenulated ribs. However, it will be noticed that 

 planicosta has on an average about 26 ribs to rotunda' $22. The 

 ribs on the post-umbonal slope of rotunda tend to be far apart and 

 show unusually sharp or large crenulations. Planicosta is finel}" 

 and evenly ribbed and crenulated. In somewhat larger shells it 

 will be foimd that the crenulation of the ribs oi planicosta become 

 obsolete basally (pi. 27, fig. i a) while in rotunda they increase 

 in size and become hoods or inverted funnels (pi. 28, figs. 4 

 and 5. 



The variety ;/, as before stated, conies up from the upper 

 Sabine beds and is abundant at Hamilton Bluff and Lisbon, Ala- 

 bama — beds of St. Maurice age. Dall regard this the same as 

 the ''Cardita hornir' of the West Coast. We have seen it in the 

 St. Maurice, from the Alabama localities and 200 yards below the 

 mouth of Bayou Negreet on the Sabine River, La. 



Specimens Jigured. — Paleont. Coll. Cornell Univ. 



Horizons. — Midway to Jackson inclusive (in America). 



Localities from the St. Maurice stage. — Texas : Practicall}'' 

 where fossiliferous beds are found, from the Rio Grande to the 

 Sabine ; we have over 50 entries from this state in our old Texas 

 MS report. Louisiana : Hammett's Br., Monroe well, Chautau- 

 qua, near Long Pt., >^ mile S. of Alabama Ldg., Ouachita Riv- 

 er; Winona; Reid's Plantation (S. 29, 19 N., 4 W.). Mississ- 

 ippi : Wautubbee. Alabama : Hamilton Bluff, Lisbon ; base of 

 Claiborne Bluff ; Coffeeville. Ga. : Ft. Gaines. South Carolina : 

 3 and 6 miles W. N. W. of Orangeburg ; Rock}^ Swamp, 5 miles 

 S. of Springfield. 



In the Claiborne stage at Claiborne, Ala. 



Venericardia rotunda Lea, PL 28, figs. 4-7, HI. 29, Figs. 2-5. 



V. rotunda Lea, Cont. to GeoL, 1833, p. 70, pL 2, fig. 48. 



V. transversa \a.v. rotunda de Greg., Mon. Faun. Eoc. Ala., p. 212, pi. 



13, figs. 6-13. 

 ? C. siibrotunda Con., Jr. Phila. Acad., Nat. Sci., vol. i, 1848, p. 129, 



