CEPHALOPODA. 



BELEMNITES, Cuv. 



B. IMPRESSUS, U. S. 

 PI. 9, Fig. 2, and 2 a. 



Shell elongated, robust, subcylindrieal, tapering convexly to- 

 wards the point for about a fourth of its length ; upper portion 

 expanded, thin. Alveolus extending about half the length of the 

 shaft ; the cavity being divided by plates placed at short distances 

 'apart. On one side is a well-marked groove extending from the 

 tip to near the top of the shaft ; becoming nearly linear below and 

 widening out above, until it loses itself in the general swell of 

 the surface. 



From north fork of Cottonwood Creek, southwest of Horsetown, Shasta County ; 

 collected by Messrs. Brewer and Reinond. 



One fragment of an alveolus was discovered by myself at Mount Diablo in the 

 gray limestone, associated with Ammonites Ittmondii and Inoccramus Piochii. This 

 is, I believe, the most southern locality of the species yet known. It is only found 

 in the older division of the Cretaceous (Div. A.). 



Figures, natural size. The section is taken from the point marked a, on the 

 large figure. 



(58) 



