ARNOLD— THE PALEONTOLOGY AND STUATIGIUI'HV OF SAN PEDRO. 123 



straigliter ventral maro;iii, ami a more evenly rniiiidetl anterior extremity than 

 T. trapezoidex. 



This species is I'oiuul in only one narrow stratum of tlie San Pedro Pliocene. 

 This stratum outcrops near the base of Deadman Island, and also on the top of the 

 ridge at the head of the railroad grade in the southeastern part of San Pedro. It is 

 the predominating species in this one stratum. 



Pliocene. — Eagle Prairie, Humboldt County (Cooper): San Pedro (Arnold). 



Miocene. — Oregon (Cooper): Blakely, near Seattle, Washington (Arnold). 



Family XV. PANDORIDiE. 

 Genus Pandora. 



Shell inequivalve, thin, pearly inside; valves close, attenuated behind ; right valve flat, with 

 a diverging ridge and cartilage furrows ; left valve convex, with two diverging grooves at the hinge; 

 pallial line slightly sinuated. 



Subgenus Kennerlia Carpenter. 

 Hinge ossicle thin; radiating ribs on the right valve. 

 Type, Kennerlia hicarinata Carpenter. 



47. Pandora (Kennerlia) bicarinata Carpenter. 



Plate XVIII, Fig. 2. 



Kennerlia bicarinala CPR., Brit. Assn. Rept., 1863, p. 638; Proc. Zool. Soc, 1864, p. 603. 



Trvon, Syst. Conch., Vol. Ill, 1884, p. 143. 

 f Pandora bUirata Coii., Cooper, 7th Ann. Rept. Cal. St. Min., 1888, p. 257. 



Shell small, planoconvex, oval, thin; umbones minute, about one-third length from anterior 

 end; anterior and posterior dorsal margins straight, making an angle a little less than 160 degrees 

 at the umbo; ventral margin arcuate, rounding upward at each end and meeting dorsal margins in 

 angulated turns; two posterior submarginal ridges run from the umbo to the extremity in the convex 

 valve; surface sculpture and hinge as in K.Jilosa. 



Dimensions. — Long. 14 mm.; alt. 9 mm.; diam. 3 mm.; umbones to anterior extremity 

 4 mm.; to posterior extremity 10 mm. 



This species is closely related to K.jilosn, but is distinguishable by its broader, 

 shorter shell, rounded rather than beaked posterior extremity, and more nearly 

 central umbones. Probably the same as Pandora hilirata of Conrad. 



One left valve from the lower San Pedro series of Deadman Island, which is 

 figured, and is now in the possession of Delos Arnold. 



Living. — Catalina Island (Carpenter). 



Pleistocene.— Sfin Pedro (ArnoM): Santa Barbara (Cooper). 



