8 PALAEONTOLOGY OF CALIFORNIA. 



gulated; concave above, convex on the side; suture very indis- 

 tinct. Surface marked by ten or twelve large, rounded, radiating 

 ribs, crossed by square elevated ribs, with sometimes smaller 

 ones interposed ; on the upper or concave portion of the whorl 

 are six or seven fine linear revolving ribs ; of the large revolving 

 ribs, three or four only appear on the upper whorls, the body 

 volution showing about fourteen. Aperture narrow; inner lip 

 thinly incrusted; outer lip acute on the edge, thickened behind; 

 posterior sinus narrow, deep, oblique, bordered by a thickened 

 rim and almost adjoining the suture. 



Figure, nearly four times the length of the specimen. 



Locality : Not common, in the Post-Pliocene of Santa Barbara. 



Specimens resembling this, but differing a little in the minute details of sculp 

 ture, were found by Dr. Cooper, in dredging off the shores of Santa Catalina 

 Island. They should probably be placed under the same specific name. 



RANELLA, Lam. 

 R. Mathewsonii, n. s. 



PI. 2, Fig. 13. 



Shell moderate in size, robust, sub-compressed; spire high; 

 number of whorls unknown; suture strongly impressed, bordered 

 by a small, though abrupt truncation of the succeeding whorl; 

 varices prominent, rounded, continuous. Mouth small; inner 

 lip heavily incrusted; canal abruptly recurved. Surface marked 

 by numerous, rounded, longitudinal ribs, crossed by square re- 

 volving ribs, with smaller ones interposed, and with flat inter- 

 spaces. 



Figure, natural size. 



Locality and position : From the Miocene, south of Martinez; a single specimen 

 found by Mr. Mathewson. 



This shell can be at once distinguished by its compact form and the alternating 

 revolving ribs. No allied species, either fossil or recent, has been found in Cali- 

 fornia. 



