176 University of California Publications in Geology [Vol. 11 



Family Muricidae Tryon 

 Genus MUREX Linnaeus 

 MUREX (OCINEBEA) SOBEANTENSIS, n. sp. 

 Plate 23, figure 3 

 Type specimen 11234, Coll. Invert. Palae. Univ. Calif., loc. 1164 



Shell heavy, medium in size, fusiform ; number of whorls five or six ; spire 

 acute. Body whorl about two-thirds the height of shell; sutures obscurely 

 appressed. "Whorls strongly and regularly convex. Surface sculptured by about 

 ten longitudinal, rounded ribs or frills, which extend entirely across the whorls 

 of spire but not onto the anterior end of body whorl. Surface also covered by 

 medium coarse, spiral ribs, the alternate ribs being the stronger except on anterior 

 end of body whorl where ribs are about equal in prominence ; interspaces between 

 ribs very narrow. On the body whorl are about twenty-five, and on the spire 

 about ten of these spiral ribs. Canal fairly long for this genus ; anterior end 

 broad. Aperture not exposed. 



Dimensions. — Type specimen: height of shell, about 26 mm.; height of body 

 whorl, 20 mm. ; greatest width of body whorl, 11 mm. 



Occurrence. — University of California localities 127 and 1164. Type, a wax 

 impression. 



This species somewhat resembles Murex dalli B. L. Clark, 141 a 

 species found in the San Pablo Group. Both have about the same 

 number of transverse ridges and the spiral sculpturing is quite simi- 

 lar. The latter species differs from the former in that the spire is 

 higher, the body whorl is not so ventricose, the anterior end of the 

 canal is more attenuate, being cut off more obliquely in the region 

 of the imperforate umbilicus. Probably the most striking difference 

 between the two species is that the sutures on M. sobrantensis are 

 appressed, while on M. dalli they are depressed. 



M. sobrantensis also resembles M. topangensis Arnold, 142 a species 

 common in the Monterey horizon in the southern part of the state. 

 The whorls on the latter species are angulated and subtabulate above 

 the sutures; on M. sobrantensis the whorls are regularly convex. 

 Also, on M. topangensis there are fewer longitudinal ridges or frills, 

 the frills being more sharp and crested. 



141 For original description see Univ. Calif. Publ., Bull. Dept. Geol., vol. 8, 

 no. 2, p. 501, pi. 67, figs. 4, 9, 1915. 



142 F or original description of Murex topangensis, see Proc. Nat. Mus., vol. 32, 

 pi. 43, fig. 4, 1907. 



