ARNOLD — THE PALEONTOLOC.Y AND STRATIGRAPHY OF SAN PEDBO. 137 



each valve, of which the anterior ones are shorter and may be concrescent or free and pustular ; 

 interior of valves commonly shows radial striatioii; and valves frequently distorted. 



Type, Kellia suborhiculdik (Moiitngii). 



68. Kellia laperousii Denkuijeti. 



Plate XVIII, Figs. 7 and 7«. 



Kellia laperousii Desii., Carpenter, Brit. Assn. Rejjt., 1863, p. 643. Keep, West Coast Shells, p. 

 178, 1S92. Williamson, Proc. U. S. Nat. Mus., Vol. XV, 1892, p. 191. Dall, Trans. 

 Wagner Inst. Sci., Vol. Ill, Part 5, 1900, p. 1155. 



Shell of medium size, suborbicular, convex, thin; umbones slightly anterior, not prominent; 

 surface sculptured by fine incremental lines which are slightly variable as to prominence; no lunule; 

 each valve with one very prominent cardinal tooth ; right valve with two posterior laterals, left with 

 one ; hinge-area lacking between cardinal and lateral teeth; muscle-impressions not distinct. 



Dimensions. — Long. 23 mm.; alt. 19 mm.; diam. 11 mm. 



Di.-jtiiigiiiishable from K. siihorhicalarh by its larger size and less convexity. 

 These two species may be recognized by their thin, snborbicular shells, and the lack 

 of a hinge-area in the region of the umbones, the vacancy at first giving the impres- 

 sion that tlie hinge-area has been broken. Specimens identified by Dr. Dall. 



Rare in lower San Pedro series of San Pedro and Deadman Island. One 

 perfect valve from the Pliocene at Deadman Island. Found also in the Pleistocene 

 of Spanish Biglit, San Diego. The specimen figured is from the lower San Pedro 

 series at Deadman Island, and is now in the collection of Delos Arnold. 



Living. — Puget Sound to Monterey (Carpenter). 



Pleistocene. — San Pedro (Arnold): San Diego (Arnold). 



Fliocene. — San Pedro (Arnold). 



69. Kellia suborbicularis Montagu. 



Plate XVIII, Figs. 1 and la. 



Kellia suborbicularis MoNT., Testacea Britannica, pp. 39, 564, PI. XXVI, fig. 6, 1804. Carpenter, 

 Brit. Assn Rept., 1863, p. 643. Trvon, Syst. Conch., Vol. Ill, p. 220, PI. CXX, 

 fig. 2, 1884. Keep, West Coast Shells, p. 177, 1892. Williamson, Proc U. S. Nat. 

 Mus., Vol. XV, 1892, p. igi. Dall, Trans. Wagner Inst. Sci., Vol. Ill, Part 5, 

 1900, p. II 55. 



Shell small, suborbicular, deeply convex, thin; beaks small, slightly anterior; surface orna- 

 mented with fine lines of growth which become somewhat irregularly constricted near margin, 

 roughening the surface; no lunule; margins smooth; hinge and teeth as in K laperousii. 



Dimensions. — Long. 8.4 mm.; alt. 7.4 mm.; diam. 5.8mm. 



Distinguishable from K. laperousii by smaller size and greater convexity. 

 Specimens identified by Dr. Dall. 



Rare in lower San Pedro series of San Pedro and Deadman Island. The 



( lij ) December 31, 1902. 



