132 CALIFORNIA ACADEMY OF SCIENCES. 



Oue nearly perfect right valve from the lower San Pedro series at Deaclman 

 Island was obtained by Mrs. Oldroyd, is figured in this paper, and is now in the 

 collection of Mrs. Oldroyd. Later another valve was found at the same locality by 

 Delos Arnold. 



Living. — Puget Sound to Santa Barbara, 40 to 60 fathoms (Carpenter). 



Pkisioceue. — San Pedro (Oldroyd; Arnold). 



Family XXXVIII. SAXICAVID^. 



Genus Panopea Menard. 



Shell equivalve, thick, oblong, gaping at each end; ligament external, on prominent ridges; 

 one prominent tooth in each valve; pallial sinus deep. 



Afya glycymeris Born, is a characteristic species. 



135. Panopea generosa Gould. 



Panopea generosa Gld., Proc. Bost. Soc. Nat. Hist. \'ol. Ill, 1850, p. 215. Wilkes' Exped., 



p. 385, PI. XXXIV, fig. 507, 1852. 

 Glvcimeris generosa Old., H. & A. Adams, Gen. Rec. Moll, p. 350, 1853. Cpr., Brit. Assn. 



Rept., 1863, p. 637. Gabb, Pal. Gal, Vol. II, p. 89, 1869. Cooper, 7th Ann. Rept. 



Cal. St. Min., 1888, p. 241. Keep, West Coast Shells, p. 209, fig. 178, 1892. 



Williamson, Proc. U. S. Nat. Mus., Vol. XV, 1892, p. 183. Dall, Wagner Inst. 



Sci., Vol. Ill, Part 4, 1898, p. 830. 



"Shell large, rather thin, nearly eqnilateral, the beaks slightly anterior, the dorsal and 

 ventral margins in the full grown shell parallel and nearly straight, the pedal margin evenly rounded, 

 the nymph narrow, and the attached edge of the ligament very short ; the pallial sinus wide 

 and shallow. 



"Dimensions. — Long. 182 mm.; alt. no mm.; diameter 60 mm." 



Dr. Dall gives the above description of a living, typical P. generosa Gould 

 from Puget Sound. In the same paper (Tertiary Fauna of Florida, Trans. Wagner 

 Inst. Sci., Vol. Ill, Part 4, p. 831) he describes two new varieties of this same species 

 which he thinks have constant differences enough to warrant the separation. Variety 

 soUda Dall has a heavy, somewhat arcuate, shell, strong nymph, a ligamentary 

 attachment twice as long as in the typical form, and a deep pallial sinus. This and 

 the typical form are found from Puget Sound to San Diego. Variety glohosa Dall 

 has a short, thin, inflated shell with the beaks nearer the anterior end, which is ex- 

 panded and rounded in the pedal region; opposite margins not parallel; pallial sinus 

 small and wide. Found at head of Gulf of California. 



Dall also classes together Mya abrupta Con. and Glycimeris estrellnna Con., of 

 the Miocene of California and Oregon, and differentiates them from P. generosa Gld. 

 under the name P. estrellana Con. 



Two imperfect valves from the upper San Pedro series at Los Cerritos were 

 identified by Dr. Dall as typical P. generosa. 



Rare in the Pliocene and lower San Pedro series at Deadman Island; and in 



