158 AXEL A. OLSSON 



Pecten (Pecten) vogdesl Arnold Plate 20, figures 4-4b 



Pecten dentatus G. B. Sowerby, 1835, Proc. Zool. Soc. London, p. 109 (not P. dentatus 



J. Sowerby, 1829).— Sowerby, 1842, Thes. Conch., vol. 1. Pecten, p. 49, No. 11, 



pi. 15, figs. 105, 106 (Santa Elena, probably incorrectly). 

 Pecten (Ewvola) cataractes Dall, 1914, Nautilus, vol. 27, p. 121 (new name for P. 



dentatus G. B. Sowerby). 

 Pecten (Pecten) vogdesi Arnold, 1906, U. S. Geol. Survey, Prof. Paper 47, p. 100, pi. 



33, figs. 1, la; pi. 34, fig. 1. (Pleistocene, San Pedro, Calif.). — Hertlein and 



Strong, 1946, Zoologica, vol. 31, pt. 2, p. 57. — Durham, 1950, Mem. Geol. Soc. 



America, No. 43, p. 61, pi. 8, figs. 4, 6. 

 Pecten (Janira) vogdesi Arnold, Grant and Gale, 1931, Mem. San Diego Soc. Nat 



Hist., vol. 1, pp. 228, 229, pi. 3. figs. 3a, 3b. 

 Pecten (Pecten) excavatus Arnold, 1906, op. cit., pp. 134, 13S, pi. 46, figs. 1, la, lb (not 



of Anton, 1839). 



Shell large (altitude 70 to 100 mm.), slightly longer than high, in- 

 equivalve, the right valve being convex, its umbone projecting above the 

 hinge line, the left valve concave, equilateral, and with more or less serrate 

 margins. Ribs in the right valve about 20; these are wide, low and rounded, 

 broader than high, separated by narrower interspaces, their surface smooth 

 except for incremental lines which loop across them. Ribs in the left valve 

 about 19; these are narrow, squarish, flat-topped, about equal in width to 

 their interspaces, sometimes longitudinally sulcated or ridged, interspaces 

 flat-bottomed, usually with a well-developed mid-rib, the surface sculptured 

 by numerous fine, sharp concentric lines, more marked in the interspaces. 

 Ears subequal, the right anterior with a byssal notch. Color salmon or 

 salmon-pink, the left valve usually darker. 



The type of P. vogdesi is a shell from the Pleistocene of San Pedro, 

 California. Arnold considered it as distinct from the Recent species which 

 he identified as P. excavatus Anton, a Chinese and Japanese species. All 

 later writers agree that the fossil and Recent forms belong to the same 

 species. Although Sowerby described P. dentatus as from Santa Elena, 

 this locality citation is perhaps erroneous, due to mixed labels. The present 

 writer has seen no authentic specimens south of Mexico. 



Range — Magdalena Bay, Lower California, Gulf of California to Pan- 

 ama. For records see Hertlein and Strong. 



Pecten (Pecten) pemlus, new species Plate 20, figures 3-3c; 



Plate 21, figures 3, 3a 



The shell is small or of medium size, seldom exceeding 40 mm. in 

 height, thin. The right valve is strongly convex, its curvature nearly that 

 of a half circle whose greatest convexity lies just above the middle, the 

 surface of the umbone sloping downward to an appressed beak. Ribs of 

 the right valve number about 22, almost obsolete near the beak, strengthen- 

 ing across the middle zone and generally mesially grooved on the ventral 

 portion, their interspaces concave and flattened. The left valve is smaller, 

 rather deeply depressed or flattened in the middle, its lateral submargins 

 elevated, flaring and smoothish. Ribs on the left valve are fewer in number, 

 usually 17 or 18; these are narrow, simple above, widening a little ventrally 

 and separated by much wider interspaces, each of which generally carries an 

 intercalary riblet. Surface of both valves, if well preserved, is uniformly 

 covered with close-set, raised concentrics which loop up and down across 

 the ribs and their interspaces. In the interior, the external ribbed sculpture 



