66 TERTIARY AND QUATERNARY PECTEN8 OF CALIFORNIA. 



Pecten (Chlamys) fucanus Dall. 



PI. X, figs. 1, 2, and 2a. 



1898. Pecten (Chlmnya) fncaniM Dall, Trans. Wagner Free Inst. Sci., vol. 3, pt. 4, 1898, p. 704, pi. 2fi, 



fig. 7. 

 1904. Pecten (Vlilamyx) fucanm Dall, Harrinian Exped. Repts., Alaska geology, Neozoic invert. 



fossils, p. 113. 



Description. — Adult shell averaging nearlj' 100 inillimeter.s in altitude, aljout 

 as long as high, inequivalve (the left being the more convex), equilateral, 

 moderately thin, and with nearly smooth margins. Right valve with from 14 to 

 17 more or less unequal, prominent, rather squarish, radiately striate ribs, between 

 which (especially the anterior and posterior ones) are occasionally intercalated 

 small riblets; inter.spaces unequal and averaging somewhat narrower than the 

 ribs; whole surface of disk sculptured by rather prominent lines of growth and 

 a fine subsidiary tessellation; hinge line longer than one-half length of disk; ears 

 equal in length; the anterior rather narrow and sculptured by 1 prominent radials 

 and tine, imbricating, incremental lamella; the posterior rectangularly truncated 

 and sculptured by more, but less prominent radials and tine concentric lamellfe; 

 byssal notch profound. Left valve usually having 1.5 or 16 unequal, prominent, 

 convex-topped ribs, the median one generally being stronger than the rest, with 

 the second or third one from it on each side only a little less prominent; the 

 prominent ribs, especially the median one, is generally surmounted by elevated 

 imbricating .scales; the otiier ribs are simply radially striated, as are the inter- 

 spaces, which often carry one or more elevate.d riblets; the submargius are radially 

 threaded, as are the subequal ears, which are rectangularly truncated, and also 

 bear marked concentric lamella; the fine subsidiary tessellation is also present on 

 well-preserved specimens of this valve. The resilial pit is of moderate size, and 

 the cardinal edge is deeply grooved parallel to and just below the margin. The 

 interior of Ijoth valves reflects the external ribbing. 



Dimensions. — Alt. 8.5 mm.; long. 80 ram.; convexity of right valve 5 mm.; of 

 left valve 1.5 mm.; hinge line 50 mm. 



The difference between the convexity and riblting of the two valves, together 

 with the variation in size, shape, and ornamentation of the individual ribs of the 

 same valve, are the prominent characteristics of this species. It is not closely 

 allied to any other species of Chlamys, but, instead, shows in its sculpture some 

 affinity to certain species of Patinojyecten. 



The type of P. fucanus (U. S. N. M., No. 107790) is the mold of the exterior 

 and interior (a cast of the former being PI. X, fig. 2) of a left valve which was 

 found by Mr. J. S. Diller in the Miocene sandstone on the coast just east of 

 Clallam Bay, Clallam County, Wash. It was associated in the sandstone formation 

 with the following species: Sigaretus sp., Crepidula sp., Dentaliuvi sp., Mytilus 

 sp., Mactra or Spisula sp., Venericardia sp., Nucula (cf.) decisa Conrad, Leda sp., 

 Tellina (cf.) arctata Conrad, Tellina sp., Chione sp. 



The writer found R fucanus at several localities (U. S. Nat. Mus. localities 

 4074:, 4077, 4081, 4082) on the coast between Clallam Bay and the mouth of the 

 Pysht River, 7 miles farther east. At all of these places it was associated with 



