150 CALIFORNIA ACADEMY OF SCIENCES. 



Distinguishahle from /'. carditoides by its siiiiiller size, narrower form, ihiiiiu r 

 shell, and coarser sculpture. Specimens of this same species in the State Rluscinu 

 collection at the University of California, Berkeley, are labeled P. coynata Adams. 

 Specimens identified l>y Dr. Dall. 



Rare in the lower San I'edro .sorie.s at JJcadniaii Island, and the upper San 

 Pedro serie.s at Los Cerritos and San Pedro. 



Living. — Mazatlan to Pern (Carpenter). 



Pleistocene. — San Pedro (Arnold; Blake.) 



Pliocene (?). — Los Angeles City (Williamson). 



97. Petricola (Petricolaria) cognata C. B. Adams. 



Pctricola cognala C. B. Ads., Cat. Panama Shells; Ann. N. Y. Lye. Nat. Hist., Vol. V, 1852, 

 p. 510. Cpr., Brit. Assn. Rept., 1856, p. 363; Proc. Zool. Soe., 1863, p. 367. 



Shell of medium size, much elongated, transverse, convex, thin, equivalve; beaks small, near 

 anterior extremity, turned forward, slightly elevated; anterior extremity short, evenly, pointedly 

 rounded; posterior extremity long, evenly, pointedly rounded; surface of shell, anterior to a line 

 running obliquely backwards from the beaks, sculptured by ten or eleven prominent, narrow, 

 squamosely spined, radiating ridges; surface posterior to this line ornamented by finer radiating lines; 

 rather prominent incremental lines over the whole surface; hinge of left valve consists of a curved, 

 saddle-shaped process of two teeth, one of which is bifid; hinge of right valve smaller and straiglitcr 

 with less prominent division of teeth. 



Dimensio7is. — Long. 36 mm.; alt. 10.5 mm.; diam. 10 mm.; beaks to anterior extremity 

 6 mm.; to posterior extremity 30 mm. 



The line of demarkation between the line and j)rominent radiating sculpture 

 in this species is not marked as in the Pholadid"' . Distingui.shable from P. denticulatn 

 by more prominent scul]tture anteriorly, longer shell, more prominent hinge-teeth and 

 more anterior beaks. P. coijnata is close to the Atlantic /''. /Jioladifornm. Some 

 authorities, notably Carpenter, unite the two form.s. 



Rare in the upper San Pedro series at the lumber yard at San Pedro and 

 at Deadman Island. 



Living. — San Pedro to Panama (Dall, mss.). 



Pleistocene. — San Pedro (Arnold). 



Supcrfamily TELLIXACEA. 



Family XXX. TELLINID.E. 



Genus Tellina Linnc. 



Subgenus Mcerella Fischer. 



Shell small, compressed, hardly folded, acute behind, rounded in front, with feeble, concentric 

 sculpture; left laterals obsolete; no interior radii; the sinus long, coalescent with the pallial 

 line below. 



Type, Tellina donacinn (Linne). 



