502 



University of California Publications in Geology [Vol. 8 



of the spire there are four of the major revolving ribs, on the body 

 whorl there are eight or nine of the major ribs. On some of the speci- 

 mens examined there are very well-defined varices ; sometimes there 

 is a varix on the outer lip, sometimes, one or two varices are found 

 posterior to this ; on none of the specimens examined do the varices 

 extend up on the whorls of the spire. Outer lip thickened internally, 

 on which are rounded to elongate den ti dilations. Aperture elongate, 

 semilunar; inner lip heavily encrusted; canal short, straight, narrow 

 and deep ; umbilicus subperf orate. 



Dimensions. — Type specimen : height, about 31 mm. ; height of body 

 whorl, 32 mm. ; maximum width of body whorl, 27 mm. 



Occurrence. — In Upper and Lower San Pablo Group, University of 

 California localities 409, 1-192. 363, etc. 



MUEEX (OCINEBEA) SELBYENSIS, n. sp. 

 Plate 67, figures 2, 5, and 7 

 Shell rather small to medium in size, heavy, subfusiform; apex 

 acute; number of whorls live or six, all strongly and regularly con- 

 vex. Spire about half the height of the body whorl; sutures slightly 

 appressed. Surface of shell sculptured by medium revolving ribs, the 

 interspaces between which are usually wider than the ribs; in each 

 interspace there is a riblet. Below the suture for a short distance the 

 revolving ribbing tends to be obsolete; this is quite noticeable on the 

 body whorl and on the lower whorl of the spire. On each whorl of 

 the spire there are three, sometimes four, of the major revolving ribs, 

 the inter-ribs being very faint or obsolete altogether ; on the body 

 whorl there are eleven or twelve of the major ribs, the inter-ribs being 

 rather prominent ; on the canal the major ribbing and the interribbing 

 are almost indistinguishable. Surface of shell also covered by eight 

 or nine fairly heavy, longitudinal ribs; these are narrower and more 

 distinct on the whorls of the spire than on the body whorl ; on the 

 body whorl these longitudinal ribs are usually rather broad, being 

 prominent on some specimens, while on others they become almost 

 obsolete ; on some specimens the longitudinal ribs are grooved or 

 split ; this irregularity of the ribbing appears to be for the most part 

 confined to the body whorl. Peristome broadly ovate ; outer lip some- 

 times thickened, dentate internally; inner lip strongly incrusted. 

 Canal short, straight, very narrow to closed. Columella subperf orate. 



