1 H^ 



RECENT PECTENS. 



1845 Perten e.ccavatns Anton, Philippi, Ablnld. und B^chr. Conchyl. vol. 1. p. 201, /V./™, pi. 2, 



tier 1 1845 (also erroneously reports this species from China). 

 184.5. P<.,to» «Wamte Valenciennes, Voy. Venus 1846 pi. 19, fig. 1. 

 1853. Vola denUUa Sowerby, H. and A. Adams, Gen. Rec-^ Mo 1 ^oL 2, 18o3, p. oo4. 

 1863. Ja.ura dentala Sovverby, Carpenter, Brit. Assn. Kept 18b. p. 64... 



1869. Janira derUata Sowerby, Gabb, Pal. Cal., so\.2 1^69 1. U4_ _^ Sp„ndvlu. 



1888 Pecten {Vola) de„taU,s Sowerby, Kiister and Kobelt, Conch.-Cab., s-.l. 1,, pt. ., . l . 



und Pecten, sp. 112, p. 155, taf. 44, figs. 1 and 2. 

 1S8S. ,/.»;.„ -/.»m;a f^owerby. Cooper Seventh Ann. Kept. Cal. St, Mm., 1S88, p. .44, (L.tea.n.u 



1897. P.ir»«« sowerby, Verrill, Trans. Conn. Acad. f-'^f'\^ J'' j., ^^^ 



1903. Pecten {Pecten) dmlatm Sowerby, Arnold, Mem. Cal. Acad. Sc, noI. 3, p. 104, pi. 1-, h.-. 

 1 and lo. 

 i>.«.m>^^>«.-Sbell averaging about To .niUimeters in altitude, .lightly longer 

 than hioh/inequivalve, plano-convex, equilateral, and with more or le.s,s coarsely 

 exrate'n^rgin ; sides concave above. Right valve very convex, the d.sk near 

 he apex projecting above the hinge line; ribs 22 or J^3, evenly convex, much 

 broader than high and separated by inter,spaces which have only the nnportance 

 of impressed lin:^s; surface smooth except for incren.ental lines vvh.ch loop do... 

 ward on the tops of the ribs; hinge line greater than one-halt length of d sk, 

 Irs equal convex, rectangularly truncated; anterior with two or three obsolete 

 "d a r ridges, and concentric sculpture; posterior genet-ally with concentric 

 culptui-e onlv. Left valve concave, ornamented by 22 or 23 promtnent, rath r 

 narrow squarish, flat-topped ribs, which are sometimes longitudinally faintl. 

 "icatJd or ridged; interspaces slightly wider than ribs, dat-bottomed and each 

 containing a prominent, rounded intercalary riblet; surface sculptured by nu.ner- 

 ous tine, sharp, regular concentric lines, which appear most prominent ,n he 

 spaces between tht ribs and riblets; ears equal, concave, laterally rectangular 

 and sculptured by tine, sharp, incremental lines and two or three more or le.ss 

 ;;LTnent radiating ridges, 'color salmon to salmon-pink, the left valve being 



*^' ^Jn.hn,.~A\t. m mm.; hinge line to ventral margin 5^. mm.; k>ng. 67 

 mm • hi....e line 35 mm.: diameter 25 mm.; umbonal angle (left valve) .ts . 



'This Is the living repre.sentative of a genetic group which compri.ses /-. 

 keepi P. rogdesi, and P. excavatus. Beginning with the oldest in the series, 

 F J.-e./>;. and advancing chronologically, the right valve becomes more convex, 

 the lateral areas, which in P. keej^l are very broad, become narrower, the ribs 

 become more numerous, narrower, and higher, the interspaces correspondingly 

 narrower, the hinge line relatively longer, and the ears more curved 



P. excavaPus is of the same shape as the Japanese ^ecxe. I la^ueaPu, 

 Sowerby, which has fewer, but sqiiarer, broader ribs on the right valve. This 

 last species has been reported from the Tertiary of Japan by Doctor Brauns n 

 his Geology of the Environs of Tokio." -P Uqueati^. has been erroneously 

 cited bv Reeve from California " (Dall). j , , i ^ 



Cooper mistook the Hat valve of P sfmrnm for P excavatm^ '^''^ }f''^':'^ 

 a specimen in the State Museum collection at the University ot California, 



>.Mem. Univ. Tokio, No. 4, 1381, p. 48, pi. 7, fig. 31. 



