528 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. aaau. 



NEW MIOCENE SPECIES AND VARIETIES. 



OSTREA ELDRIDGEI, new species. 



Plate XLII, figs. 2 and 2a. 



Description. — Shell about 150 mm. in length, inequivalve, the left 

 ver}' convex, the right flat or slightly concave. Left valve with 

 incurved umbo; a prominent, falcate, evenly convex ridge extends 

 from near the umbo to the margin of the left valve posteriorly; sur- 

 face of this valve and ridge foliaeeous and more or less inclined to be 

 fluted. Left valve approximately flat, with foliaeeous sui'face. 



Dimensions. — Longitude, 147 mm.; latitude, 87 mm.; diameter (dis- 

 tance through both valves), 82 mm. 



Notes. — This species is distinguished from the other Tertiary oysters 

 of the California Tertiary bv the prominent posterior ridge and 

 incurved umbo of the left valve. The species has the external appear- 

 ance of a Gryjyhmi. Named in honor of the late Mr. George Homans 

 Eldridge, of the U. S. Geological Survey. The type was associated 

 with Turritella inesiana Conrad at the Grimes Canyon locality. 



Type.—C2±. No. 164966, U.S.N.M. 



Locality. — Elkins ranch, east of Grimes Canyon, near Fillmore, 

 Ventura County, California. (G. H. Eldridge.) 



Horizon. — Lower Miocene, supposed equivalent of the Vaqueros 

 formation. 



MYTILUS MATHEWSONII Gabb var. EXPANSUS, new variety. 

 Plate XLIII, fig. 2. 



Description. — Shell wedge-shaped, rounded behind, curved; poste- 

 rior margin curved, semiangular in middle, anterior margin more 

 nearly straight; beaks terminal, blunt; surface sculptured by irregular 

 concentric lines and ridges of growth and by line radiating strite. 



Dimensions. — Longitude, 105 mm.; latitude, 50 mm.; diameter of 

 both valves, 60 mm. 



Notes. — This variety diflfers from the typical form in being some- 

 what smaller, relatively broader, and with straighter anterior margins. 

 The fine radial striation is also said to be lacking in the typical form. 

 It is associated at the t3^pe locality with Scutella fairhansl'i Merriam, 

 Ostrea near titan Conrad, and Pecten sespeensis var. hydei Arnold. 



%)d.— Cat. No. 164968, U.S.N.M. 



Locality.— ^^^v Torrev Canyon oil wells, southwest of Piru, Ven- 

 tura County, California. (G. H. Eldridge.) 



Horizon. — Lower Miocene, supposed equivalent of the Vaqueros 

 formation. 



