TERTIARY FOSSILS. 57 



DOSINIA, Scopoli. 

 D. MATHEWSONII, n. s. 



PL 15, Fig. 16. 



SHELL nearly circular, excavated under the beaks, about the 

 size of D. Dunckerii, but of nearly the form of D. ponderosa, con 

 vex, thin. Beaks small, pointing strongly forward. Surface nearly 

 smooth in the middle, marked by lines of growth which become 

 strongly developed towards the two ends. Lunule large, lanceo 

 late and slightly impressed. 



Length, 1.9 inch ; width, 1.8 inch ; height of one valve, .25 inch. 



From the Miocene of Martinez; and at Griswold's, on the road from San Juan 

 to New Idria. 



With the outline of Dosinia ponderosa, and the peculiarity of its surface, this 

 shell has about the average size of D. Dunckerii. It is more convex than either, 

 much thinner than the first, and wants the rounded anterior prolongation and ra 

 diating lines of the other. The lunule is proportionally longer and more slender 

 than either. It seems to he peculiar to the Miocene ; D. ponderosa appearing, of 

 full size, and for the first time, in the Pliocene. The other species has not been 

 found fossil in California. 



TAPES, Megerle. 

 T. STALEYI, Gabb. 



PI. 16, Fig. 17, 17 a. 



(Dosinia id., G. Pal. Gal., Vol. 2, p. 24.) 

 (Tapes id., G. Pal. Cal., Vol. 2, pi. 7, fig. 42.) 



A single worn specimen, from which this species was originally described, de 

 ceived me as to some of its characters. It has a true Tapes hinge, and the surface 

 is crossed by very numerous, minute radiating ribs. It is not unfrequently a 

 little larger than the specimen figured ; the pallial sinus is very deep, and rather 

 narrow. 



The ribs are of the same character as those of T. straminea, but are at least four 

 times as numerous as the most finely costate varieties of that species that I have 

 ever seen. 



PAL. TOL. II. 9 



