118 



University of California Publications. 



[Geology 



Occurrence : — The locality is about two and one-half miles 

 south of Martinez, on the west side of the road to Walnut Creek. 

 It occurs only in the upper Martinez beds. 



Discohelix Calif ornicus, n. sp. 



Pl. 12, Fig. 9. 



The shell is of the typical discohelix form. The number of 

 whorls is five. The characteristic angles are sharp, especially on 

 the outer whorl. The first whorl is more prominent on the upper 

 than on the lower side. The upper side of the shell is flat to 

 slightly concave. The surface is smooth and the aperture nearly 

 square. 



Dimensions: — The specimens are not perfectly circular, due 

 to distortion. The maximum diameter is 21 mm. and the mini- 

 mum diameter of the same specimen 19% mm. The width of the 

 outer whorl is 4.5 mm. 



Occurrence: — It is most common about four miles to the 

 southwest of Martinez, on the west side of the Del Hambre Canon 

 road. It occurs in the lower beds only. 



Turitella conica, n. sp. 



Pl. 13, Fig. 2. 



The shell is moderate in size and rather robust. The number 

 of whorls present is nine. They increase rapidly in size and are 

 flat to slightly convex on the outer face. The suture is impressed. 

 Each whorl is marked by five distinct, equidistant, revolving 

 ribs, the lower three of which are very prominent. Between these 

 are several fine striae. The aperture is subquadrate. 



Dimensions : — The maximum length of the specimen described 

 is 18 mm. The maximum diameter is 7.5 mm. 



Occurrence : — It is common on the west side of the road be- 

 tween Martinez and AVanut Creek, about three miles south of 

 Martinez. 



Xenaphora zitteli, n. sp. 



Pl. 12, Fig. 8. 



Three specimens have been found. The largest of these has 

 seven nearly flat whorls. The spire is low. The base is nearly 

 flat. The aperture is obliquely quadrilateral. A line joining the 



