88 TERTIA.KT AND QUATERNARY PECTENS OF CALIFORNIA. 



interspaces; surface sculptured by fiue iru-remental lirulje which loop back over 

 the tops of the ribs; hinge line over one-half length of disk; eai's subequal; 

 anterior with -i or 6 prominent radials. posterior with one or two less prominent 

 ones; both ears sculptured by fine incremental lines; byssal notch rather 

 prominent. Left valve a little less ventricose than right and with ribs narrower 

 and more sharply convex above and the interspaces relatively broader; ears as 

 in right valve. 



Dimensionn. — Alt. 4.3 mm.: long. 50 mm.: hinge line 28 mm.; diameter 

 28 mm. 



This species is probably allied to P. circular !n and P. clrcularis var. 

 iv-qmsulcatus, ))ut may be distinguished by its fewer and narrower ribs and longer 

 hinge line. 



The type (U. S. N. M. No. 5912) is labeled " Neah Bay, Washington," and 

 was collected by Lieut. J. G. Swan. The beds in the immediate vicinity of 

 Neah Bay were found by the writer to be almost entirely unfossiliferous, so that 

 it is probable that P. nsahensh, instead of coming from Neah Bay, comes from 

 some of the fossiliferous strata farther east, possibly from those in the vicinity 

 of Clallam Bay. 



RANGE. 



Miocene. Clallam County, near (i) Neah Baj-, Washington (J. G. Swan). 



Pecten I Plagioctenium) pabloensis Conrad. 



PI. XXVII, figs. .5, 5a, 6, 6o, and 7. 



1857. Pecten pahloemis CoxxtaA, Pac. R. R. Rept., vol. 6, pt. 2, 1857, p. 71, pi. .'?, fig. 14. 

 1888. Peclen 2)(Moenxi'< ConroA, Cooper, Seventh Ann. Rept. Cal. St. Min., 1888, p. 2.58 (in part). 

 1898. Pecten (? Plagioctenlum) pabloens-i^ Conrad, Dall, Trans. Wagner Free Inst. Sci., vol. 3, pt. 4, 

 1898, p. 703. 



DewripttDit. — Shell averaging about 35 millimeters in altitude, about as high 

 as long, oquivaive, equilateral, tliin, only slight!}- ventricose. and with smooth 

 margins; sides sloping at a low angle and quite prominently concave above. 

 Right valve with 18 to 2(» square, flat-topped, radiating ribs, which are narrower 

 and less distinct laterally and become more feeble as the i>eriphery of the disk 

 is approached; interspaces about as wide as the ril)s. flat l)ottomed and often 

 separated from the principal ribs by impressed lines wiiicii give the interspaces 

 the appearance of bearing intercalary riblets; whole surface of disk sculptured by 

 tine concentric lines and, in some instances, more or less prominent lines showing- 

 interrupted growth; hinge line somewhat longer than one-half length of disk; 

 anterior ear slighth' longer than posterior, deeply notched, and ornamented by 

 4 or 5 coarse radiating ridges and sharp, raised incremental lines; po.sterior ear 

 slightly concave behind, and covered by numerous incremental lines and several 

 obsolete radiating ribs. Left valve similar to the right except that in some cases the 

 ribs are slightly more rounded above, and the looped or wav}^ concentric lines 

 are more conspicuous; ears similar to those of the right valve except that the 

 anterior one lacks the deep byssal notch. Hinge as in /-". cireularh except that 

 the cardinal crura are very faint, while the auricuhir ci-ura are (|uite prominent. 



