128 TERTIARY AND QUATERNARY PECTENS OK CALIFORNIA. 



1888. Janira Horidii Hinds, Cooper, Seventh Ann. Kept. C'al. St. Min., 1S.H8, p. 244 ( /'. hniiphilli and 



P. atimrimi in part). 

 1898. Pecten (Pecten) cliec/ensw Dall, Tran.s. Wagner Free Inst. Sei., vol. 'A, ]>t. 4, l.SRs, p. 71(i. 

 1908. Peclen lUegenm Dall, Arnold, Mem. Cal. Acad. Sci, vol. 3, 1908, ji. lOfi, pi. VI, fig. .5. 

 1904. Pecten diegmisis Dall, Keep, West. Am. shells, p. .'-i9. 



I)escrij>ti(iii. — Shell averagino' about GU iiiilliiiioter.s in altitude, lonuer than 

 liigh, inequivalve, plano-convex, of nearly- .so, e([uilateral and with .smooth margins: 

 base evenly rounded; sides slightly concave above. Right valve .somewhat convex 

 (more pronounced near the umbo), and ornamented by about 22 or 23 prominent T-rail- 

 shaped ribs, flattened, and generally longitudinally ridged or sulcated on top, which 

 overhang deep, narrow, flat-liottomed interspaces; whole surface scidptured by 

 numerous line, sharp, incremental lines; hinge line slightly less than one-half length 

 of disk; ears equal, slighth' convex, rectangularly truncated, sculptured liy tine, 

 .sharp, incremental lines; anterior ear with small bvssal notch. Left valve flat or 

 nearly so, generally concave nejir apex, ornamented by 21 or 22 prominent, narrow, 

 convex-topped ribs, which are separated by concave-bottomed interspaces about 

 equal in width to the ribs: whole surface prominently sculptured by numerous 

 regular, tine, sharp, concentric, raised lines; ears concave, convexly truncated, and 

 ornamented by the same concentric sculpture as the disk. C'olor. red and reddish 

 brown, the left valve always l)eing much darker than the right. 



Diiiievsidiix. — Alt. .58 mm.: long. t)4 mm.: hinge line 2'.i nun.; diameter i;-! mm.; 

 umbonal angle (left valve) 95-. 



This species is distinguishable from its nearest relative, and prol)able precursor. 

 /'. steanixii, b^' the smaller number and greater height of its (/'. ///,(/, /ix/'x) ribs, and 

 relativeh' somewhat longer hinge line. The ribs of P. dit;<j<m><ix have .sometimes 

 as many as three longitudinal sulci. Mrs. Oldroyd has two specimens taken from 

 fishermeirs nets at San Pedro, which measure over 150 millimeters ((! inches) in 

 length, and are exceptionally high colored for this species. 



Living. Monterey (Button; Mrs. Lambert and others); San Pedro (Oldroyd; Ra_v- 

 mond); (_";italnm Island. 10 fathoms (Arnold): San Diego (Raymond). (In all 

 cases dredged.) 



Pleistocene. San Diego (Hemphill). 



Pecten (Nodipecten) subnodosus Sowerby. 



PI. LII, tig. 1; PI. LIIl, figs. 1 and \a. 



188.5. /"((/en .sifinorfosMs Sowerby, Proc. Zool. .Soc, 183.5, p. 109 



1842. Pecten subnodosns How^rhy , Thes. Conch., vol. 1, pt. 1, 1842, p. 112, pi. 1.5, fig. 97. 



18.52. Pecten xahnodom» Sowerby, Reeve, Conch. Icon., vol. 8, Monog. (lenus Pecten, Xov., 1852, pi. 4. 



fig. and sp. 20. 

 18(i7. Pecten intermedium Conrnd, Am. Jour. Conch., vol. 8, 1807, p. 7 (rfrfcDall, 1898). 

 1888. Pecten snbnodosus Sowerby, Kiister and Kobelt, Conch. -Cal)., vol. 17, pt. 2, Spondylus und Pecten. 



no. 71, p. 112, taf. 32, fig. 3. 



1897. Lyropecten sidmodosus Sowerby , Verrill, Trans. Conn. Acad. Sci., vol. 10, p. 64. 



1898. Pecten (I\^odi pecten) siihnodosus Sowerby, Dall, Trans. Wagner Free Inst. Sci., vol. 8, pt. 4, 1898, 



p. 710. 



