MEXICAN BOUNDARY LINE. 165 



TURRITELLA LEONENSIS. 



Plate XXI, Figure 1, a, h. 



Volutions sub-angular, each witli three distant, large, crenulated, revolving ribs, and an 

 intermediate crenulated line ; spire rapidly tapering to the apex ; body volution large, rounded 

 at base, which has four or five fine revolving ribs. 



A limestone cast ; traces of shell show oblique longitudinal folds or ribs. 



HAMirES LARVATUS. 



Plate XXI, Figure 8. 

 Hamites larvatus, Con. Proc. Acad. Nat. Sci., vol. VII, p. 265. 



Ovate-oval, obliquely ribbed; beak and front obtusely rounded or sub-truncated; ribs oblique, 

 distant, very prominent, acute^ unequal, frequently alternated, obsolete on the back, and having 

 a tubercle on the front margin or angle ; ribs on the front thickened and obtuse ; sides of the 

 shell flattened, and the rib margin nearly rectilinear ; smaller ribs generally without a distinct 

 tubercle. 



I have amended the former description of this species from the specimen here figiired. In the 

 Arkansas specimen the ribs are alternated, the smaller one being without a tubercle ; but the 

 former has three equal ribs with the tubercle on each, and above them is the smaller rib without 

 it. Traces of the shell show annular strias. 



Localities. — Leon Springs, Texas ; White river, Arkansas. 



