1915] 



Clark: Fauna of the San Pablo Group 



495 



rounded spiral ribbing with moderately deep interspaces which are 

 nearly as wide as the tops of the ribs. On the body whorl there are 

 about seven of these coarse spiral ribs, the ribbing being obsolete on 

 the canal. On each whorl of the spire there are three of the revolving 

 ribs. Outer lip sharp ; inner lip smooth and rounding ; canal medium 

 long, straight and narrow. 



Dimensions. — Height, 25 mm. ; height of body whorl, 18 mm. ; 

 greatest width of body whorl, 13 mm. 



Occurrence. — The writer so far has seen only one specimen of this 

 species ; this was found by Dr. John Buwalda (after whom it is named) 

 to the southeast of the town of Walnut Creek in the Upper San Pablo 

 Group, University of California locality 1263. 



CHEYSODOMUS CIEEBOENSIS, n. sp. 

 Plate 68, figure 1 



Shell large, thick, spire high, acute; whorls regularly and rather 

 strongly convex with deeply depressed sutures ; number of whorls 

 six or seven ; surface of whorls sculptured by coarse, flat-topped, re- 

 volving ribbing, a wide rib alternating with a narrower rib, the inter- 

 spaces between which are about equal to the width of the minor rib. 

 Toward the anterior end of the body whorl the two sets of ribbing 

 become nearly equal. On the whorls of the spire there are usually 

 four of the major revolving ribs, sometimes five; on. the body whorl 

 there are eight or nine of the major revolving ribs. Interspaces be- 

 tween revolving ribs narrower than the tops of the major ribs ; canal 

 moderate in length; outer lip sharp, crenulated internally; inner lip 

 smooth. 



Occurrence. — This species is a very common form from the Lower 

 San Pablo Group, University of California localities 409 and 1532. 



CHEYSODOMUS DIABLOENSIS, n. sp. 

 Plate 68, figure 3 



Shell fusiform ; spire high, with four to five whorls ; apex acute. 

 Body whorl a little less than two-thirds the height of the shell. Sutures 

 impressed. Surface sculptured by fine, sharp, narrow, revolving ribs. 

 On the body whorl there are nineteen of these ribs, while on each 

 whorl of the spire there are nine or ten. These ribs tend to go in 

 pairs, every other interspace usually being wider than the ones next 

 to it, the wider interspaces being nearly twice as broad as the tops of 



