144 PALAEONTOLOGY OF CALIFORNIA. 



numerous, flattened, revolving ribs, with narrow interspaees. 

 Aperture linear; inner lip incrusted. A single small fold in 

 advance, on the columella. 



Figure, natural size. Usually found smaller. 



Localities: Martinez ; Texas Flat, Placer County; Clayton; Cochran's, east 

 of Mount Diablo; San Diego; and Alizos Creek, near Fort Tejon. 



This is one of the most common Cretaceous fossils in the State, and is one of 

 the few species that range through both divisions of the formation represented 

 here. Through an inadvertence, the lithographer has deprived the summit of its 

 proper pit-like character. 



MEGISTOSTOMA, N. Gen. 



Shell shaped like Philine, thin, slightly enrolled; body volu- 

 tion very much expanded, produced above. Aperture occupying 

 nearly all of the front surface. Columellar lip thickened, flat, 

 rather heavily incrusted. 



The peculiar character on winch this shell is separated from 

 the genus Philine (Bullcea, Lam.), is the flat, thickened, and 

 incrusted columella, that genus having no columella, and the 

 oral surface of the penultimate whorl being regularly rounded. 



M. STRIATA, 11. S. 

 PI. 21, Fig. 108, and 108 a, b. 



Shell flattened, involute, oval; body whorl composing nearly 

 the whole bulk of the shell. Mouth broadly expanded; outer 

 lip produced posteriorly in a broad, rounded process; inner 

 lip flattened, and heavily incrusted by a longitudinally striate 

 layer of shell. Surface marked by numerous square, thread- 

 like and slightly elevated strise, which are usually grooved in the 

 middle ; these are crossed by lines of growth. 



Figures, natural size, and a magnified view of the surface. 

 Locality: All of the specimens I have seen were collected by Mr. Mathcwson, 

 about a mile northeast of Martinez, in Division B. 



