ARNOLD — THE PALEONTOLOGY AND STRATIGRAPHY OF SAN PEDRO. 10 I 



aspect of anterior extremity. Tliis fossil form of Coiinul's is separated from the living 

 G. iyitermedia by Dr. Dall. Specimens identified by Dr. Dall. 



Rare in up|>er San Pedro series of San Pedro, Los Cerritos, Deadman Island 

 and Crawfisli Geori;'e's. Found also in the Pleistocene of Pacific Beach, San Diego. 

 The specimen figured is from the upper San Pedro series at San Pedro, and is now 

 in tlie collection of Delos Arnold. 



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

 (Arnold). 



20. Glycymeris septentrionalis Middendorf. 



Plate XVIII, Fi.^. 10. 



Pedunciilus septenbionalis MiDD., Carpenter, Brit. Assn. Rept., 1856, p. 219. 



Shell of medium .size, nearly circular, convex, thick; umbones central, not prominent; sur- 

 face sculptured with rather faint ridges of growth and radiating grooves, which are more or less 

 interrupted by the ridges; triangular ligamental area between umbones divaricately striated; hinge 

 with a semicircular row of transverse teeth; muscle impressions subequal; interior of margin 

 crenulated. 



Dimensions. — Long. 30 mm.; alt. 32.2 mm.: diam. 22 mm. 



Distinguishable from G. barbarensis by its evenly rounded outline. Differs 

 from Carpenter's living P. septentrionalis var. subobsokta by having larger, thicker 

 shell, greater convexity, and more pronounced sculpture. Specimens identified by 

 Dr. Dall. 



Rare in upper San Pedro series of San Pedro, Los Cerritos, Crawfish George's, 

 Deadmau Island and Long Beach. The specimen figured is from the upper San 

 Pedro series at San Pedro, and is now in the collection of Delos Arnold. 



Living. — Ukaraok Island, Alaska coast (Carpenter). 



Pleistocene. — San Pedro (Arnold). 



Subfamily ARCING. 

 Genus Area ( Linne) Lamarck. 



Shell oblong, subquadrangular, gaping anteriorly or inferior))-; hinge linear, straight, formed 

 of a large number of small pectinated teetii; ligament external, inserted upon a lozenge-shaped area 

 between the beaks, beaks high, rather wide apart; muscular impressions very distinct; pallial im- 

 pression entire. 



Type, Area nocn Linne. 



21. Area labiata Sowerhy. 

 PL.VTE XVIII, Fio. 4. 

 Area labiata Sby. , Carpenter, Brit. Assn. Rept., 1856, pp. 310, 363. 



Shell of medium size and thickness, arculate below, straight above, with small but promi- 

 nent presocoelous beaks; anterior extremity evenly rounded; posterior extremity angular near base, 

 a rather prominent convex angle running from beak to lower portion of the posterior extremity; right 



