1915] 



Clark: Fauna of the San Pablo Group 



481 



LEPTOTHYRA DANVILLENSIS, n. sp. 

 Plate 65, figures 11 and 12 



Shell conical, about as high as the greatest width of the body whorl ; 

 whorls regularly and quite strongly convex. Number of whorls six ; 

 base of body whorl flattish but with no sharp line of angulation be- 

 tween the sides and the base ; suture deeply depressed. Whorls of 

 spire sculptured by eight or nine fairly prominent, narrow, concentric 

 ribs with interspaces nearly twice as wide as the tops of the ribs ; on 

 the sides of the body whorl there are eight concentric ribs ; the base 

 of the whorl is sculptured by thirteen or fourteen concentric ribs, 

 which are finer than those on the sides of the whorl ; aperture round. 



This appears to be the first species of this genus reported from 

 the Miocene of the "West Coast. There are three Recent species of 

 Leptothyra on the coast of California ; these are L. bacula Carpenter, 

 L. carpenteriana Pilsbury and L. paucicostata Dall. Of these three 

 species, L. danvillensis most resembles L. carpenteriana. It differs 

 from that species in that it is larger and the spire is higher; the base 

 is flatter ; the concentric ribbing is more regularly interspaced ; the 

 interspaces are wider ; the sculpturing on the base of the body whorl 

 is finer. 



Dimensions. — Type specimen: height of shell, 11 mm.; greatest 

 width of body whorl, 11 mm. 



Occurrence. — In the San Pablo Group about one mile to the south 

 of Danville to the west of the County Road, University of California 

 locality 323. 



CALLIOSTOMA BICARINATUM, n. sp. 

 Plate 65, figures 14 and 19 

 Shell conical; apex acute; body whorl about as high as spire; sides 

 of whorls convex ; sutures depressed. Upper part of body whorl sculp- 

 tured by about thirteen elongate, oblique nodes, some of which on the 

 type specimen are rather obscure ; between the base and the oblique 

 nodes are two prominent spiral ribs, which are separated from each 

 other with an interspace about equal to the tops of the ribs; the upper 

 spiral rib has a tendency to be nodose. Base of body whorl flat, at 

 right angles to the sides and sculptured by four fairly prominent re- 

 volving ribs, the inner two of which are closer together than the outer. 

 Whorls of spire sculptured similarly to body whorl, except that on 

 each whorl the lower of the two side spiral ribs is covered by the whorl 



