TERTIARY FOSSILS. 25 



Figure, natural size. 



Locality and position: From the Pliocene on Mark West Creek, a branch of 

 Russian River, Sonoma County ; discovered by Mr. V. S. Staley, after whom it 

 is named. 



This shell can be at once distinguished from D. ponderosa, which is quite com 

 mon in the Tertiary of California, by its less circular outline, the beaks being 

 placed more in advance, by its being more convex, by its less strongly marked 

 lunule, a differently shaped hinge, and its smooth surface. 



D. CONRADI, n. s. 



PI. 5, Fig. 43. 



(D. alia, Con.; Proc. Philada. Academy Nat. Sci., 1856, p. 315; not D. alia, 

 Dkr.; nor D. alia, Con.; P. R. R. Rep., Y. 5, p. 320, pi. 2, f. 2: D. alia, Con.; 

 P. R. R. Rep., Yol. 6, p. 71, pi. 3, fig. 13, 13 a.) 



SHELL rather small, thin, very elongated; beaks prominent, 

 margins rounded. Lunule deep. Surface marked by concentric 

 lines of growth. 



Figure, natural size. 



Localities: San Eniidio Ranch, near Fort Tejon; also "Monterey" (Dr. New- 

 berry). From the Miocene. 



The original of Mr. Conrad's figure having been a distorted specimen, I have 

 prepared the present drawing for the purpose of showing the true outline of the 

 species. Unfortunately his name was preoccupied, and I have therefore dedi 

 cated the species to the pioneer of Tertiary Palaeontology, not only for California 

 but of the Atlantic States as well. 



TAPES, Megerle. 



? T. TRUNCATA, n. 8. 

 PI. 7, Fig. 44. 



SHELL large, thin, transverse; beaks in advance of the middle, 

 pointed forwards; anterior and posterior ends nearly equal, 

 rounded ; base broadly and regularly convex. Surface marked 

 by numerous small, radiating ribs, nearly obsolete posteriorly. 



PAL. VOL. II. 5 



