52 TERTIARY AND QUATERNARY PECTENS OF CALIFORNIA. 



\aive more couipi'essetl than right, siinilarly sculptured, V>ut with botii ears 

 slightly o1)li({uely truncated, the anterior one showing- a broad .shallow notch. 

 Hinge and muscle scars similar to /'. ixJandlois. 



I)t)iieh.si<inK. — Alt. 34 nnu.; long. 33.5 mm.; hinge line 19 mm.; diameter I'i 

 nmi. (right valve 7 mm., left valve 5 mm.). 



The general outline and convexity of all the shells of this species appear to 

 he about the same, but the ribs are (|uite variable, as regards both number and 

 shape. In most cases the ribs are evenly rounded and about equal in width to 

 the interspaces, but in some cases they are ridgelike and narrower than the 

 interspaces. In .some specimens a few of the ribs become dichotomous distant 10 

 or 15 nnllimeters from the umbo, and small riblets are intercalated in a few of 

 the interspaces at about the same distance. One specimen is contracted at a 

 distance of about 30 millimeters, and shows several intercalaries beyond the line 

 of contraction. Some of the specimens of P. landesi remind one somewhat of 

 /-'. meiiihriincmts Morton, from the Eocene of North Carolina, although the latter 

 has more and narrower ribs, and is ornamented by finei' iinl)ricating sculpture 

 than the former. /'. lamlesl is distinguishable from /'. jiraaeus by its relatively 

 longer disk and fewer l)ut more prominent, regular, and less imbricated ribs. It 

 is distinguishable from /'. calkhif-i by its smaller size when adult, fewer but 

 more elevated ril)s, and relatively much shorter hinge line. 



P. lamlcsi is found quite abundantly in a dark-greenish sandstone bed that 

 outprops about lOO yards west of the junction of Stillwater and Oiequa creeks 

 (Li. S. Nat. Mus. locality -lOl'J) one-fourth mile southwest of Little Falls, Lewis 

 County, Wash. It is also found in a similar matrix in the bed of Oiequa Creek 

 (U. S. Nat. Mus. 4024-), 1 mile north of the first locality. It is associated in this 

 formation with a characteristic Eocene fauna, among which are the following 

 species: Vciiei'icanUd planiamta Lamarck, Thmcia dtller! Dall, Cramatellites sp., 

 Meretrix sp., (M.reii sp., Pteria (cf.) liinidu Conrad, Card'iain '1 .sp., Barhatla sp., 

 Olycymei'ls sp., Corhidu sp., CalUsta .sp., Turritella (cf.) uvasana Conrad, JFiisus 

 4 sp., Ocinehra sp., Ran/dla sp., Calyptr<q>h<iru» sp., Lunatia sp., Turhhidla (?) sp., 

 Murcx2 sp., Conus a^.^ Cassis up., Trifoniuiii sp.. Dented lu.m (cf.) rvwy^vv' Gabb, and 

 JVcmfdiix sp. This horizon is proba!)iy upper Eocene, possibly above the Tejon. 

 Named in iionor of Prof. Heni'v Landes, Seattle, Wash. 



Eocene (probably upper). Vicinity of Little Falls, Lewis County, Wash. U. S. 

 Nat. Mus. locality 4ulii; 40-24. (Arnold.) 



Pecten (Chi.amys) i'koavus n. sp. 



PI. II, tigs, fi, 7, ami S. 



Descrqjfion. — Shell averaging about 50 millimeters in altitude, much higher 

 than long, compres.sed, subequivalve, and equilateral, except for the ears; base 

 regularly rounded; margins smooth; sides straight and forming an acute angle at 

 the umbo. Left valve with numerous more or less unequal, narrow, thread-like, 

 imbricated ribs, between which are occasionally much finer intercalaries; interspaces 

 about as wide as ribs, channeled and flat botti)med; whole surface of disk and 



