ARNOLD — THE PALEONTOLOGY AND STKATIGEAPHY OF SAN PEDRO. 183 



the upper Sau Pedro series at Deadman Island, San Pedro, and Los Cerritos. Found 

 in the Pliocene at Packard's Hill, Santa Barbara. 



Living. — Puget Sound to San Diego (Dall). 



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



Pliocene. — Santa Barbara; San Fernando (Cooper): San Pedro; Santa Bar- 

 bara (Arnold). 



Genus Panomya Gray. 



Shell solid, large, irregular, with a single cardinal tooth under the beak in each valve; the 

 pallial line of unconnected rounded impressions. 



Type, Panopea {Mtja) norvegica Spengler. 



136. Panomya ampla JJaU. 



Panomya ampla Dall, Trans. Wagner InsL Sci. , Vol. Ill, Part 4, 1S98, p. 833. 

 Panopea jiorvegica Midd. (pars.) Mai. Ross., Vol. Ill, p. 78, PI. XX, fig. 11, 1849 (not of Spengler) 

 (^fide Dall). 



Shell large, irregularly subquadrate, ventricose, thick; beaks subcentral, incurved, small, 

 sharp, elevated; anterior extremity rounded, projected furthest above middle; posterior extremity 

 gaping, abruptly and irregularly truncated, with angular corners above and below; basal margin 

 nearly rectilinear; two large folds separate the shell into three parts; one fold extends to the lower 

 posterior angle from the umbo, and the other extends to the lower anterior angle from the umbo; 

 surface roughly sculptured by concentric lines and undulations; one small cardinal tooth in each 

 valve; cartilage-process rather short, projecting; pallial line of unconnected, rounded impressions. 



Dimensions. — Long. 55 mm.; alt. 38 mm.; diam. 27 mm. 



This species reminds one somewhat of a young Panopea generosa, but is 

 distinguishable from that species by the more central beaks, shorter and more 

 irregular shell, two prominent folds, and unconnected pallial line. Specimens 

 identified by Dr. Dall. 



Rare in the Pliocene at Deadman Island; several perfect valves found. 



Living. — North Pacific, Behring and Okhotsk Seas (Dall). 

 Pleistocene. — North Pacific, Behring and Okhotsk Seas (Dall). 

 Pliocene. — San Pedro (Arnold). 



Superfamily ADESMACEA. 



Family XXXIX. PHOLADID.E. 



Subfamily PH0LAD1N.E. 



Genus Zirphaea Leach. 



Shell oval, cardinal margin scarcely reflected; no accessory valves, the beaks protected by 

 a membrane; usually a thin, fugacious epidermis; anteriorly greatly gaping. 



Type, Pholas crispata Linne. 



