Clark: The San Lorenzo Series of Middle California 111 



sides of the whorls are more convex and are not so perpendicular, each 

 whorl sloping in more obliquely toward the axis. The sculpturing 

 of the two species appears to be identical, except that on the latter 

 the spiral ribbing tends to be heavier; undoubtedly they are closely 

 related species. 



TURRITELLA POETEEENSIS Weaver 



Turritella porterensis Weaver, Wash. State Geol. Surv., vol. 52, p. 73, pi. 



11, figs. 83, 84, 1912. 

 Turritelli new comb ei Arnold and Hannibal, in part, Proc. Amer. Pliilos. 



Soc, vol. 52, p. 581, 1913. 

 Turritella porterensis Weaver, Univ. Wash. Publ. Geol., vol. 1, no. 1, pp. 5, 



30, 1916; Calif. Acad. Sci., ser. 4, vol. 6, no. 2, pp. 28 and 40, 1916. 

 Occurrence. — Found at University of California locality 3051. 



TUEEITELLA PORTEEENSIS SOBEANTENSIS, n. var. 

 Plate 22, figure 1 

 Type specimen 11269, Coll. Invert. Palae. Univ. Calif., loc. 3051 

 Turritella porterensis Clark, not Weaver. Univ. Calif. Publ., Bull. Dept. 

 Geol., vol. 9, no. 2, p. 15, 1915. 

 Shell medium in size ; whorls about ten ; sides of whorls flat, sloping slightly 

 inwards ; sutures impressed. A narrow depressed area or groove at the base of 

 each whorl, in which may usnally be seen a spiral riblet ; sides of whorls sculp- 

 tured by six or seven narrow but prominent ribs, separated by interspaces about 

 equal to the ribs. 



Occurrence. — University of California localities 14, 215 and 1131. 



The details of the sculpturing of this form are identical with that 

 of T. porterensis Weaver. Weaver does not describe the riblet in 

 the depressed area at the base of each whorl but it occurs on many 

 of the specimens of that species from the type locality. The main 

 difference between the species and the variety is that on the species 

 there is a slight convexity near the base of each whorl ; this is described 

 by Weaver as being a broad angulation ; on the variety the sides of 

 the whorls are flat down to the depressed area. On some specimens 

 of T. porterensis the convexity of the whorls, as described above, is 

 almost obsolete. 



Family Cerithiidae 



Genus POTOMIDES Brongt 

 POTOMIDES (CERITHIDEA) BEANNEEI, n. sp. 

 Plate 22, figures 6, 13 and 16 

 Type specimen 11229, Coll. Invert. Palae. Univ. Calif., loc. 2754 

 Shell medium in size, fairly heavy. Spire high ; number of whorls nine or 

 ten; sutures slightly depressed, marked by a well-defined, impressed line; whorls 

 only slightly convex. Surface of shell sculptured by about thirteen or fourteen 



