58 TERTIARY AND QUATERNARY PECTENS OF CALIFORNIA. 



byssal notch not profound; posterior ear rectangularly truncated and ornamented 

 with concentric sculpture similar to that of the anterior: interior of disk 

 strengthened by nine strong, roimded, elevated, radiating I'ibs, which teriuinate 

 abruptly at a length of t! or 7 millimeters; the middle ribs are straight, but 

 occasionally the lateral ones are faintly arcuate toward the middle rib. Left valve 

 beautifully ornamented externalh- by numerous regular, thin, concentric, imbricating, 

 prominently elevated lamelhe which, sloping at an angle of about 45'- toward the 

 umbo, rise into 10 or 11 prominent, rounded, radiating pseudo-ribs, separated by 

 somewhat widei' interspaces, in nearly every one of which is an intercalated, 

 imbricated pseudo-riblet; this riblet begins only after the shell has attained a height 

 of about 1.5 to 2 millimeters: ears similarly sculptured to those of the right valve. 



Diiiun.sionn. — Alt. (type, left valve) 10 mm.; long. 9.5 mm.: hinge line 5.5 mm.; 

 diameter al)out <i.75 mm. 



This beautiful little Pecti'v appears to be allied to P. stanfordensiit, but is 

 easily distinguished from the latter by its beautifully laraellated surface, and in 

 pos.sessing 9 instead of 10 or more internal riblets. 



The type of P. daUamemis is a left valve (U. S. N. M. No. 164922) and was 

 found at locality 4100, li miles east of Pillar Point, near the mouth of the Pysht 

 River, Clallam County, Wash., where it was associated with Aturia cf. sicsac 

 Sowerby, DuUum jyetroKum, Conrad, Fiiaus sp., Natica or Imnatia, MargineUa or 

 lU'iiti) s\)., NhcuIci sp., Leila sp. (large, smooth), Telliiui {Avguhis) sp., Solemya sp., 

 Dentalki'Di Kuhstriatuin Conrad. The cotype is a right valve (U. S. N. M. No. 

 164923), is from locality 4070, Bean Point, King Countj-, Wash., and is associated 

 there with Terehratida sp., T\irriteUa sp., MargineUa or Erato sp., Natica or 

 Lanatia s^., Glycymeris sp., and Astynn sp. 



Both of the localities at which /'. claUamensi.s have so far been found are in 

 the lower portion of the Oligocene-Miocene series. 



Oligocene-Miocene. Mouth of Pysht River. Clallam County, and Bean Point, west 

 of Seattle, King County. Wash. (Ai'nold). 



Pecten (Propeamusium) waylandi n. sp. 



PL III, ligs. 4 and 5. 



Pescnpfion. — Adult shell averaging about 9.5 millimeters in altitude, somewhat 

 longer than high, subcircular, equivalve, equilateral, thin, somewhat convex in 

 youth, but becoming more compressed with age; margins smooth. Disk of right 

 valve sculptured by luuiierous line lines of growth and numerous, more or less 

 obsolete, tine radiating lines; hinge line equal to about one-half the length of the 

 disk; ears subequal; anterior arcuate in front and faintly sculptured concentricall\' 

 by sharp lines and radially by faint ridges; byssal notch narrow and shallow; 

 posterior ear slightly obliquel\' truncated and sculptured by faint radial ridges 

 and tine, sharp, concentric lines; interior of disk strengthened by S subequal, 

 strong, narrow, smooth, conve.x-topped riblets, which are widely separated and 

 which terminate abruptly at about 6 to 8 millimeters from the umbo; these 



