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Cerithium fairbanksi n. sp. (PL I, Fig. 12.) 



Shell large, turreted, (first two or three whorls wanting); next 

 rounded, with about nine vertical ribs, very prominent at middle, and 

 crossed by six or seven revolving grooves. Three anterior whorls so 

 broken that the vertical ribs are gone, except at sides where they 

 appear as sharp varices, the eight or nine grooves crenulating their 

 edges, and well separated by the sutures; the revolving grooves extend 

 to base of shell at edge of canal (which is broken off). Base with four 

 or five unequal ribs. 



Mouth sub-oval, outer lip crenulate; columella, . Length, nearly 



2 inches; breadth, 0.85; mouth, 0.40; width, 0.35. This was one of the 

 tropical forms, and more ornamented than the C. mexicanum Gabb, 

 from Sonora. It seems likely that varices extended the whole length 

 on each side, as in C. echinatuvi, but were not continuous. Only one 

 specimen found, half imbedded in hard rock, and the surface much 

 worn off. It was discovered by Mr. Fairbanks, at the west side of 

 Point Loma, San Diego, in the stratum of Cretaceous A. 



Potamides carbonicola n. sp. (PI. I, Figs. 14 to 19.) 



Form columnar, slowly tapering (first whorls eroded); third or fourth 

 strongly sculptured, with twelve to fifteen subvertical ridges, curved 

 toward the left, and crossed by three revolving ridges, causing a cancel- 

 lated surface. The ridges vary in development on different parts of 

 one shell, as well as on different specimens. Sometimes one and some- 

 times the other set of ridges has the most strength, and often one 

 or two of the revolving ones being higher than the third, causes an 

 angular projection either at middle of whorl or along the suture, the 

 whorls being flat when all are equal, and twelve or more in number- 

 No thickening of lips or varices shown in the specimens. Length, 1.50 

 inch; breadth, 0.50 to 0.75; mouth, 0.12 long and wide. 



This shell, like other Potamides, evidently inhabited a muddy bay, 

 in which fragments of coal were mixed with mud, and the matrix now 

 contains them in great quantity, the shells being often filled with the 

 black mixture. 



They were also gregarious, as is P. californica in our bays, but from 

 their fragility it is very difficult to obtain whole ones. Several are 

 figured to show the variations of surface. 



Head-wall of "California Coal Mine," near Huron, Fresno County, 

 east slope of Mt. Hamilton range. Cret. B, Mr. Watts. 



Potamides? davisiana n. sp. (PL I, Fig. 13.) 



First three whorls convex, turbinate, smooth; the next six turreted, 

 increasing rapidly by wide, flattened expansions of the upper surface 

 of whorls, with a sharp raised carina half-way between the sutures, 



