100 TERTIARY AND QUATERNARY PECTENS OF (CALIFORNIA. 



PeCTEN (PeCTEN) 8TEARNS11 Dall. 

 1>1. XXXII, fig.«. 1 anil 1". 



18H9. Janira deiitata Gabh (not Sowerby), Pal. Cal, vol. 2, 1SH9, p. 104 (in part). 



1879. PerlfiiMrarnf:!! Dall, Proc. U. S. Nat. Mus., vol. 1, 1879, p. 14. 



1888. Jiinira denitiUt Cooper (not Sowerby), Seventh Ann. Kept. Cal. St. Min., 1888, p. 244 (in part). 



1898. Peclp.ii (I'erten) stearmii Dall, Trans. Wagner Free Inst. Sci., vol. 3, ])t. 4, 1898, p. 70t>, pi. 26, tig. 5. 



1900. Void sji. indet., Merriam, Bull. Cal. St. Min. Bureau, No. 19, 1900, p. 222, table 4. 



1903. Perten {Pirttti) utearmH Dall, Arnold, Mem. Cal. Acad. Sci., vol. o, IWA, \\ 106, pi. 12, (ig. :i. 



/},'scr/j)t/"ii. -Slu'll of inodium size, .-^uhcii'ciilar, iiiCMiuivalve, coiu-avo-convex, 

 thin; right valve slightly convex, with al)out 2<i regular, even, .square ribs, se))arated 

 hv channeled interspaces somc^vvhat narrower than the ribs; the top surface of each 

 ril) is flattened with a broad, shallow groove in tiie middle, with one or two faint 

 rihlets on each side of the groove: whole surface co\ered with concentric laiuelhe 

 which are iiuich liner and about twice as crowded as those of the left valve; left 

 valve flattened or concave, with about 24 regularly rounded, vaulted, e^en ribs, 

 separated by slightly wider channeled interspaces; the whole surface covered with 

 fine, sharp, concentric, regular lamella^ a little looped l)ackward over the tops of 

 the ridge; ears of this valve concave, with obsolete radiating ridges, and tine, con- 

 centric lamelhe; ears of right valve subequal, arched, covered with crowded, 

 elevated lamella?; byssal notch verj^ small. 



Dimensions. — Alt. 62 mm.; long. 71 mm.; diameter 14 mm.; hinge 2.5 mm. 



According to Doctor Dall this is the precursor of /'. (licf/eiisis, from wiiich it 

 differs bv having 5 or ti more rib.s, which in the adult have a con.spicuous medial 

 sulcus. 



/'. xtiurnsii, so far as known, is conhned to the Pliocene. It is quite abundant 

 at Pacific lieach, near San Diego, where it is associated with /'. Jnnlci/i, J', henqi- 

 hilli., Opalia varicostata^ O. anoinala, Smla stearnsii, JrWfen parmelcei. and other 

 uniciue forms. In a well at 8an Juan Capistrano it was found by Watts associated 

 with Tnrritella coojH-ri, Vcin-ricdrdia roifricosa, Ann frilinrdfn, ]V<(x!«i niendieii, etc. 

 Two left valves have been foiuid in the Pliocene at Deadmaii Island, near San Pedro. 



Pliocene. Temescal Canyon, Santa Monica Mountains. Los Angeles County (Watts, 

 Rivers); San Pedro (Arnold); San .Tuaii Capistrano, Orange County (Watts); 

 Pacific Beach, near San Diego (Hemphill, Stearns. Dall, Arnold); Third street 

 tunnel, Los Angeles (Hamlin). 



Pecten (Pecten) vogdesi n. sp. 



PI. XXXIII, figf'. 1 and Ik; I'l. XXXIV, tig. 1. 



1888. .Tiuiird ilmlaui Cooper, Seventh Ann. Kept. Cal. St. ISIin., 1888, p. 244 (Quaternary record.s). 

 1903. Pecten (Pecten) dentntnK .\rnold, :\Ieni. Cal. Acad. Sci., vol. 8, 190H, p. 105 (Pleistocene record). 



Drsrripfion. — Shell similar to /-". ercafutiis, except averaging larger and with the 

 following difierences: Right valve, somewhat less convex, has lit or 2(> ))roader, flatter 

 ribs, which are separated by relatively luoader interspaces that occasionally show 

 faint intercalarv riblets or faint longitudinal striations. Left valve with fewer ribs 



