1915] 



Clark: Fauna of the San Pablo Group 



477 



ficial appearance of Gari alata Gabb is that of a Sanguinolaria." The 

 study of the dentition leaves no doubt of the generic determination. 



8. alata differs from S. nuttallii Conrad, a Recent species, as fol- 

 lows: the shell differs in outline; it is equivalved, while S. nuttalli 

 is inequivalved ; the nymph plate is longer and more conspicuous. 



Gabb in his description of this species described the anterior end 

 for the posterior. 



Occurrence. — In the Lower San Pablo Group, two miles east of 

 Kirker Creek, north of Mount Diablo, University of California locality 

 62. Also on the west side of Mount Diablo, on south side of Shell 

 Ridge, University of California locality 351. So far this species has 

 been found only in the Lower San Pablo. 



SANGUINOLARIA?, sp. 

 Plate 61, figure 13 



Shell medium in size, elongate, subovate in outline ; beaks incon- 

 spicuous, anterior to the middle; anterior dorsal edge slightly convex; 

 posterior dorsal edge nearly straight ; anterior and posterior ends 

 evenly rounded ; ventral edge long and regularly arcuate ; surface of 

 valve very slightly convex. Shell smooth, except for more or less 

 prominent incremental lines. Ligamental groove rather short, with a 

 nymph plate extending along its entire length ; the nymph plate is a 

 little higher than the dorsal edge ; it is somewhat of the type of the 

 nymph plate on 8. nuttallii Conrad, a Recent species on this coast ; 

 hinge plate unknown. 



Dimensions. — Length, 27 mm. ; height, 18 mm. ; diameter of one 

 valve, about 2 mm. 



Occurrence. — One specimen known, from the Upper San Pablo 

 Group of the San Pablo Bay section, University of California locality 

 1617. 



SOLEN PERRINI, n. sp. 

 Plate 44, figure 2 



Shell straight, rather heavy ; posterior extremity broadly rounded, 

 anterior extremity truncated, the margin of which joins the posterior 

 dorsal edge at an angle of a little more than 90° ; well-defined groove 

 or flexure parallel and close to the anterior dorsal edge. (This flexure 

 on some specimens is more pronounced than on others.) 



