1915] 



Clark: Fauna of the San Pablo Group 



489 



species on this coast. They differ from the latter in having the flat- 

 tened sides with the obscure shoulder on the upper part of the body 

 whorl. N . pabloensis differs from N. ocoyana in having a lower spire, 

 the top of the shell is broader, sloping down less rapidly to the obscure 

 shoulder. 



Dimensions. — Type specimen (pi. 68, fig. 12) : height, about 37 

 mm. ; greatest width, about 42 mm. ; length of aperture, 34 mm. ; width 

 of aperture, 17 mm. 



Occurrence. — In the Upper and Lower San Pablo Group, Uni- 

 versity of California localities 231, 38, 1227, etc. ; also, in the Scutella 

 breweriana zone. 



BITTIUM? PABLOENSIS, n. sp. 

 Plate 65, figure 10 



Shell medium in size; spire high, acute; whorls six or seven. On 

 the upper edge of each whorl is a rounded, slightly raised ridge or 

 rim which gives to the shell a tabulated effect; sides of whorls flat 

 below the rim ; sutures depressed. Surface covered with regular, 

 medium fine, revolving ribs with interspaces about as wide as the ribs ; 

 on the body whorl there are ten or twelve of these revolving ribs, on 

 the whorls of the spire the ribbing is obscure ; outer lip sharp. Inner 

 lip smooth; aperture oval, only slightly emarginated anteriorly. 



Dimensions. — Height, about 16 mm.; greatest width of body whorl. 

 8 mm . 



Occurrence. — So far only two specimens of this species have been 

 found ; these came from near the top of the San Pablo Group on San 

 Pablo Bay, associated with Cyrena calif ornica Gabb, Cerithium rodeo- 

 ensis, n. sp., Mytilus perrini, n. sp., Mya dickersoni, n. sp., University 

 of California localities 1617 and 1618. 



BITTIUM TBAMPASENSIS, n. sp. 

 Plate 65, figures 3 and 5 

 Shell small ; number of whorls, seven or eight, or possibly nine. 

 Sides of whorls flat, sutures impressed. Surface sculptured by about 

 twenty medium fine longitudinal ribs, the interspaces between which 

 are about as wide as the tops of the ribs. Surface also covered by 

 medium fine spiral nodose ribbing, the nodes being at the point of 

 junction with the longitudinal ribbing. On the body whorl there are 

 six of these spiral ribs ; the anterior rib is partly on the base. The 



