59 St. Maurice and Claiborne Pelecypoda 59 



This species was described from Jacksou, Miss., and is not 

 rare in the Jackson beds of Louisiana also. So far as we are 

 aware the species does not occur in the Claiborne stage, but is 

 found not unfrequently in the St. Maurice at various localities in 

 Mississippi. It appears to have suffered but few changes during 

 its long banishment from southern waters during the Claiborne 

 age, still, the Jacksonian forms are quickly separated from the St. 

 Maurice by their greater height medially, i.e. they are a httle 

 more triangular in outline, with dorsal line more flexed at the 

 beak, or not so parallel with the basal margin as is the case with 

 the St. Maurice specimens. Then too, the posterior radiating 

 lines on the latter are coarser, tending to more of a pronounced 

 alternation in size, with coarser granules. 



Type. — Donated to the Phila. Acad, by State Geologist 

 Wailes, 1855. 



Specimen fjgjires. — C. U. Paleont. Mus., (Wautubbee, Miss). 



Horizons and localities. — St. Manrice stage : Wautubbee, 

 Miss. Also at Hickory and near Enterprise, Miss. (DallJ. 

 Jackson stage : Jackson, Miss. ; Montgomery, and at various lo- 

 calities on the Ouachita River, La. 



Ledahoustonia Harris, PI- 23. Fig. 13. 



L. houstonia Harris, Proc. Phila. Acad. Nat. Sci., 1895, p. 47, pi. i, 



fig- 5- 

 L. houstonia Dall, Trans. Wag. &c.. Ill, 1898, p. 578. 



Harris's original description. — General form as figured ; concentric 

 lines scarcely discernible except where they pass over the umbonal ridge ; 

 post umbonal slope traversed by one raised line extending from the umbo to 

 near the extremity of the valve ; sometimes as many as eight or ten raised 

 radiating lines appear near the posterior sub-margin. 



Type and specimen figured. — Texas State Univ. 



Localities and horizon. — St. Manrice stage : Alabama bluff, 

 Trinity River, Houston Co. ; between Orrell's and Evergreen 

 Crossing, Elm Cr., Lee Co. ; along Elm Cr. from Orrell's to 

 Price's Crossing, Texas. Specimens observed in the Phila. Acad, 

 collection are labelled " Leda {Nuculana) subtrigona Con. ? S. 

 Carolina." 



