ARNOLD — THE PALEONTOLOGY AND STRATIORAPHY OP SAN PEDRO. 173 



This species is distinguishable from var. nuttalli by its small size, fragile shell, 

 more posterior umbo, and sharper, narrower, shorter, and more nearly perpendicular 

 interior callus. Dr. Dall in his paper on the Solenidte says that Carpenter (Brit. 

 Assn. Ropt., 18G3, p. ()3l) and Ciabb (18G8) have confounded the young of S. nuttalli 

 with this species. A large series of S. luckla from the Pleistocene shows the above 

 mentioned differentiating characteristics to be constant. Specimens identified 

 by Dr. Dall. 



Rather rare in the lower 8an Pedro series at Deadman Island and San Pedro; 

 and in the upi)er San Pedro series at San Pedro and Los Cerritos. Found also in the 

 Pleistocene at Twenty-sixth Street and Spanish Bight, San Diego. 



Living. — Monterey to San Diego (Dall). 



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



123. Siliqua patula (Dixov) var. nuttalli Conrad. 



Solecuiiiis ?iu//a//! Con.. Jduv. Phil. Acad. Sci., Vol. VII, 1837, page 232, PI. XVII, fig. 9. 

 Machcera patula, not of Dixon, Voy. Around the World, p. 335, fig. 2, 1789. Carpenter, Brit. 



Assn. Rept., 1863, p. 638 (in part). Gabb, Pal. Cal. , Vol. II, p. 89, 1869 (in part). 



Cooper, 7th Ann. Rept. Cal. St. Min., 1888, p. 248 (in pari). ? Keep, West Coast 



vShells, p. 201, fig. 171, 1892. 

 ? Siliqua patula DixoN, WILLIAMSON, Proc. U. S. Nat. Mus., Vol. X\', 1892, p. 1S5. 

 Siliqua nuttalli QoN., = 5". californica CoN. {fide Dall, Trans. Wagner Inst. Sci., \'ol. Ill, Part 5, 



1900, p. 956). 



Shell large, oblong-oval, compressed, thin, fragile; umbones a little over one-fourth length 

 from posterior end, minute; anterior end more acutely rounded than posterior; ligamental area 

 prominent, projecting beyond an equally long depression in the anterior dorsal margin; cardinal 

 teeth in right valve, four in the left; a strong, elevated callus extends over half way across the in- 

 terior of the shell from the umbo at nearly right angles with the dorsal margin. 



DimensioJis. — Long. loi mm.; alt. 39 mm.; diam. 14 mm. 



Distinguishable from S. hicicla by larger, heavier shell; distinguished from 

 I'agelus calif ornianus by the posterior position of the beaks, and by the more rounded 

 extremities. Specimens identified by Dr. Dall. 



Rare; a nearly perfect pair from the upper San Pedro series at San Pedro. 

 Found also in the Pleistocene at Spanisli Bight, San Diego. 



Living. — Mouth of the Columbia River (Conrad). 



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



Pliocene. — ? Localities. 



Miocene. — ? Localities. 



