Clark: The San Lorenzo Series of Middle California 155 



a broad, shallow sinus anterior to this ridge and parallel with it. A good right 

 valve of the species was not obtained but it seems very probable, as on many 

 species of this genus, that on this valve there would be a sinus near and parallel 

 to the posterior dorsal margin, corresponding to the ridge on left valve. Two 

 well-developed cardinals in left valve. 



Dimensions. — Length, about 50 mm.; height, about 37 mm.; greatest diameter, 

 about 23 mm. 



Occurrence. — University of California locality 1131. 



This species is quite unique, differing from most of the other 

 species of this genus in having the beaks so far anterior. 



Family Psammobiidae 

 PSAMMOBIA, aff. EDENTULA (Gabb) 

 Plate 16, figure 3 



A number of specimens of a species of Psammodia have been 

 obtained in the San Ramon formation at several localities. All the 

 specimens are too poor to permit of specific determination. The form 

 is close in outline to P. edentula Gabb, but appears to differ in some 

 minor respects ; the outline differs somewhat from the majority of 

 that species ; also, the nymph plate is not so heavy. P. edentula 

 (Gabb) 124 is a variable form, especially in outline, and for that reason 

 the writer has hesitated to describe the form from the Agasoma 

 gravidum beds as a new species. He feels, however, that it is very 

 probably a new species and will be differentiated when better material 

 is obtained. 



Family Donacidae 

 Genus DONAX Linnaeus 

 DONAX sp. mat. 

 A cast from University of California locality 1314. 



Family Solenidae Leach 

 Genus SOLEN Linnaeus 

 SOLEN .(PLECTOSOLEN) CUBTUS Conrad 

 Plate 10, figure 6 



Solen curtus Conrad, Amer. Jour. Sci., ser. 2, vol. 5, p. 433, fig. 14, 1848. 

 Plectosolen curtus Conrad, Check list Eocene Fossils N. Am., p. 8, no. 239, 

 1866. 



Enses curtus Meek, Check list Miocene Fossils N. Am., p. 12, no. 416, 1864 ; 

 Conrad, Am. Jour. Conch., vol. 1, p. 152, 1865 ; Gabb, Geol. Surv. Calif., 

 Palaeontology, p. 116, 1868. 



!2* For original description of Psammobia edentula (described as Siliquaria? 

 edentula), see Geol. Surv. Calif., Palaeontology, vol. 2, p. 53, pi. 15, fig. 11, 1869. 



