ARNOLD — THE PALEONTOLOGY AND STRATIGRAPHY OF SAN PKDUO. 10 1 



aspect of nnterior extremity. This fossil form of Coiinul's is sepiinilccl from the liviii.i; 

 G. iufermcilia hy Dr. DaH. Specimens i(lentific<l l)y Dr. Dall. 



Rare in iij)|)er Sail PeJro series of San Pe(h-o, Los Cerritos, Deadiuan Ishiiul 

 ami Crawfish George'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 the collection of Delos Arnold. 



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

 (Arnold). 



20. Glycymeris septentrionalis Middendorf. 



Plate XVIII, Fu:. 10. 



Pectunculus septetilrionalis MiDD., Carpenter, Brit. Assn. Rept., 1856, p. 219. 



Shell of medium size, nearlj' circular, conve.x, 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. 



Dislinguishable from Q. 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, 

 Deadman Island and Long Beach. The specimen figu'-ed 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 AIWIX^E. 

 Genus Area (Linne) Lamarck. 



Shell oblong, subquadrangular, gaping anteriorly or inferiorly; hinge linear, straight, formed 

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

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

 pression entire. 



Type, Area nofe Linne. 



21. Area labiata Soiverby. 

 Platk .win, Fio. 4. 

 Area labiaia Shy., Carpenter, Brit. Assn. Rept., 1856, pp. 310, 363. 



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

 nent presoccelous 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 



