126 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser- 



the external or ventral shoulder of the whorl in a double row; those of the 

 inner row have a greater lateral prominence, while the outer incline more 

 toward the plane of the keel. In shells of 3 or 4 cm. diameter these tuber- 

 cules have often a triangular appearance that is lost in older whorls. The 

 umbilical tubercules are more prominent upon alternate ribs, and are thin 

 and ridge-like in form. Above a diameter of 3 or 4 cm. the ribs become 

 depressed in their middle portion, forming only a bare connection of external 

 and umbilical tubercules in old age. 



The suture line is simple; siphonal lobe long and relatively narrow, with 

 short, narrow teeth upon the side, parallel and equal; terminal teeth longer 

 and divided; first lateral saddle broad, bifid, and having either sharp or 

 rounded, small digitations; lateral lobe broad and tapering evenly in general 

 outline, indistinctly trifid, having sharp and narrow digitations; second lateral 

 saddle liigh and little cleft, scalloped at margin; second lobe and succeeding 

 saddle small and narrow. The digitations of the suture are not always 

 regular, different septa of the same specimen showing considerable varia- 

 tion. On the whole, however, they agree with the septa figured by Meek 

 for his species. Meek seems to have noticed in the Dakota types the same 

 irregularity. The furrows along the keel of the Oregon type are compara- 

 tively shallow, as seen upon the casts. Aside from this there is no other 

 difference in the two types, unless it be a little greater thickness for those 

 from Oregon. 



Occurrence. — This species was found on the Smith 

 ranch, near Phcenix, Oregon, at whi(;h place several good 

 specimens were obtained, though from its abundance tiiere 

 it should be expected at the other localities. It belongs to 

 a horizon equivalent to that of the Lower Chico beds of 

 the Sacramento Valley. 



The types are in the collections of the California 

 Academy of Sciences. 



