ARNOLD — THE PALEONTOLOGY AND STKATIGRAPHY OF SAN PEDRO. 129 



Shell small, subcircular, ventricose, thick ; umbones slightly anterior to center, much bent 

 forward, prominent; surface sculptured by about thirteen prominent, rounded, radiating ridges, 

 which are slightly roughened by regular lines of growth; sulcations narrow; hinge area broad, short; 

 two prominent teeth in each valve, anterior short; margin closely crenulated. 



Dimensions. — Long. 12.5 mm.; alt. 13 mm.; diam. 8 mm. 



Distingui.shable by small size, coarse sculpture and heavy hinge. Common in 

 the Pliocene of Deadman Island and Timin's Point; rare in lower San Pedro series 

 of Deadman Island. Found also in Pleistocene of Pacific Beach, near San Diego; 

 and in the Pliocene of Packard's Hill and the Pleistocene near the bath-house, 

 Santa Barbara. 



Living. — Alaska to Cataliua Island (Cooper). 



Pleistocene. — Santa Barbara to San Diego (Cooper): San Pedro; Santa Bar- 

 bara; San Diego (Arnold). 



Pliocene. — San Fernando; Santa Barbara to San Diego (Cooper): San Pedro; 

 Santa Barbara (Arnold). 



Miocene. — Oregon; Foxin's, Santa Barbara County; Santa Monica (Cooper): 

 Blakeley, near Seattle, Washington (Arnold). 



Genus Lazaria Conrad. 



Shell transverse, oblong, inequilateral; beaks subanterior, radiately ribbed ; hinge with two 

 cardinal and two lateral diverging teeth in each valve, the posterior teeth being in each case much 

 elongated, the anterior short and more or less pointed, sublunular. 



Lazaria pectunculus Brug. is a characteristic species. 



56. Lazaria subquadrata Carpenter. 



Lazaria subquadrata Cpr., Brit. Assn. Rept., 1S63, p. 642; Ann. Mag. Nat. Hist., 3d ser.. Vol. XV, 

 1865, p. 179. Cooper, 7th Ann. Rept. Cal. St. Min., 1888, p. 244. Keep, West Coast 

 Shells, p. 179, fig. 152, 1892. Williamson, Proc. U. S. Nat. Mus.,Vol. XV, 1892, p. 190. 



Shell small, transverse, subrectangular, inequilateral, ventricose, thick; beaks subanterior, 

 not prominent ; dorsal posterior margin long, straight ; anterior portion abruptly truncated just in 

 front of beak; surface sculptured with heavy, squamose, rounded, radiating ridges; interior 

 margin coarsely crenulated; hinge with two lateral diverging teeth in each valve, the posterior teeth 

 being in each case much elongated, the anterior short and pointed. 



Dimensions. — Long. 10 mm.; alt. 6 mm.; diam. 5.6 mm. 



Distinguishable by its small size, rectangular outline, and coarse, squamose 

 ridges which radiate from one corner of the rectangle. Specimens identified 

 by Dr. Dall. 



Rare in the lower San Pedro series of Deadman Island and San Pedro; and 

 in the upper San Pedro series of Crawfish George's and San Pedro. 



Living. — Straits of Fuca to San Diego (Cooper). 



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



( n ) December 29, 1902. 



