134 University of California Publications in Geology [VOL. 8 



convex and not straight. The anterior and posterior dorsal margins 

 of V. aequilateralis Gabb are straight, while those of Venus(f), sp., 

 are concave and convex respectively. 



MERETRIX STANTONI, n. sp. 

 Plate 11, figures la, Ib 



Meretrix, sp. Stanton, T. W., The Faunal Relations of the Eocene and 

 Upper Cretaceous on the Pacific Coast, 17th Ann. Rept., U. S. Geolog- 

 ical Survey, p. 1042, 1896. 



Dr. Stanton in his paper on the Eocene and Upper Cretaceous of 

 the Pacific Coast describes a Meretrix, but does not give it a specific 

 name. Since this form is abundant in the basal beds north of Mount 

 Diablo and the Martinez in Lake County at Lower Lake, and is dis- 

 tinctive, it is thought best to name it specifically. Dr. Stanton 's 

 description is as follows : 



"One of the most abundant species at the locality one mile southeast of 

 Lower Lake is a venerid apparently belonging to the genus Meretrix and closely 

 resembling the original figure of M. hornii Gabb, but as Gabb discredited that 

 figure when it was published and his later figure and the specimens preserved 

 in the Academy of Natural Sciences, Philadelphia, are not at. all like it, our 

 fossils can not be identified with his species. Possibly this will prove to be 

 a new species, but I shall not venture to name it until several of Gabb 's 

 venerid species represented by conventionalized figures are better known. Shell 

 subtriangular, moderately convex; with thin test; beaks prominent, considerably 

 in advance of the middle, lunule small, deeply impressed; dorsal margin slightly 

 convex behind the beak, sloping rapidly to the narrowly rounded posterior end; 

 anterior end broadly rounded; ventral margin forming a regular curve; surface 

 marked by closely arranged, rather prominent ridges and furrows which vary 

 considerably in size. The numerous specimens collected show considerable 

 variation in relative length of the shells, but this feature does not seem 

 sufficiently constant for specific separation. The dimensions of the largest 

 specimens: Length, 43mm., height, 31mm.; convexity of single valve about 

 8 mm. The corresponding measurements of a smaller specimen of the short 

 variety are 27, 23, and 6 mm., respectively. ' ' 



M. stantoni, which is probably related to M. hornii, is more acute 

 posteriorly and the anterior end is higher above. The concentric lines 

 of M. hornii are less numerous and more prominent than those of 

 M. stantoni. This shell apears to be distinct from the short species, 

 M. dalli, described below. It is very abundant in the lower beds of 

 the Martinez formation at University of California Locality 1556, 

 Martinez Group, Mount Diablo Quadrangle, one and one-eighth miles 

 south of Stewartville in the lower beds ten feet above the Martinez- 



