ARNOLD— THE PALEONTOLOGY AND STRATIGRAPHY OF SAN PEDRO. 167 



The specimen figured is not the type, which is larger, and is in the United 

 States National Miis;eum. The specimen ligured came from tlie lower San Pedro 

 Series at Deadman Islam!, and is now in the collection of Delos Arnold. 



Living. — Monterey (Dall). 



Pleistocene. — San Pedro (Arnold). 



Genus Cumingia Soirtrbij. 



Shell transversely oval, equivalve, rounded in front, subrostrated and slightly gaping behind; 

 small, thin, often irregular in form; hinge with a spoon-shaped cartilage-pit, and a small anterior 

 cardinal tooth in each valve; two elongated lateral teeth in the right valve, less developed in the left; 

 beaks small; surface concentrically ridged; pallia! sinus very wide. 



Tyi)e, Cumingia mutica Sowerby. 



114. Cumingia calif ornica Conrad. 



Cumingia californica Con., Jour. Phil. Acad. Sci., Vol. VII, 1S37, p. 234, PI. XVII, fig. 12. Car- 

 penter, Brit. Assn. Rept., 1863, p. 640. G.\bb, Pal. Cal., Vol. II, 1869, p. 94. 

 Cooper, 7th Ann. Rept. Cal. St. Min., 1888, p. 238. Keep, West Coast Shells, p. 196, 

 fig. 168, 1S92. Williamson, Proc. U. vS. Nat. Mus., Vol. XV, 1892, p. 186. 

 = C. simi/is A. Ad. {fide Dall, Trans. Wagner Inst. Sci., Vol. Ill, part 5, 1900, 

 p. 100 1 ). 



Sliell of medium size, transversely oval, slightly ventricose, thin; umbones small, incon- 

 spicuous; anterior margin evenly rounded; posterior sloping from umbo at an angle of about 45 

 degrees, straight; posterior end somewhat obliquely truncated; surface sculptured by numerous, 

 about equidistant, sharp, narrow, concentric ridges or frills; hinge vith a triangular, spoon-shaped 

 cartilage-pit and a small anterior cardinal tooth in each valve; two elongated lateral teeth in right 

 valve, less developed in the left; pallial sinus very wide, expanded interiorly and deep. 



Dimeiuions. — Long. 24.5 mm.; alt. 18 mm.; diam. 4.9 mm. 



Resembles Macoma nasutn in general outline, but is easily distinguishable by 

 the sharp, concentric ridges. Specimens identified by Dr. Dall. 



Found in the lower San Pedro series at Deadman Island and San Pedro, and 

 in the upper San Pedro series at Deadman Island, Crawfish George's, and San Pedro. 



Living. — Monterey to San Diego; Mazatlan (Cooper): Japan (Stimson). 



Pleistocene. — Santa Barbara; San Diego (Cooper): San Pedro (Arnold). 



Family XXXII. PSAMMOBIID.E. 

 Genus Psammobia (Lamarck) Boivdich. 



Subgenus Psammobia fs. s. 



Shell elongated, more or less pointed behind; compressed; somewhat rudely concentrically 

 sculptured; the posterior dorsal area frequently sculptured diver.sely from the disc; the pallial sinus 

 elongated and for the most part coalescent below with the pallial line. 



Type, Pnammobia feroehsis Gmel. 



