PLIOCENE PECTENS. 117 



Pectex (C'hlajiys) i.awsom 11. sp. 

 PI. XLV, tigs. :! and 4. 



Dencrij^tlon. — Adult shell averaging- about 7(» inilliiueters in altitude, not a.^ lonj;" 

 as high, inequi valve, only slightly convex, ei|uilateral, ears unequal: base regularly 

 rounded; sides only slightly concave above; margins .somewhat serrate. Right valve 

 with about 18 to 20 subequal, prominent, narrow, round-topped, rugose ridges. se))a- 

 rated by .somewhat wider interspaces, in each of which runs a single more or less 

 rugose riblet; .some of the ribs are occa.sionally medially sulcated or dichotomou.s; 

 surface sculptured by numerous irregular incremental lines, which give the ribs a 

 squamose appearance when they are unworn; ears unequal, the anterior with three 

 or four rather prominent rugose radials and numerous incremental lines; the poste- 

 rior with several less prominent radials, and incremental sculpture; liyssal notch 

 rather profound. Left valve with 9 or 10 prominent narrow, round-topped, rugose 

 major ribs, between each two of which there is a single minor rib similai' to and 

 almost equaling in prominence the major ribs; a single thread-like intercalary is 

 visible in most of the interspaces; surface sculptured as in the right valve; cars 

 similar to those of right valve except that tliere is no prominent notcli l)etwc(>n tiie 

 anterior one and the disk. 



Dimensions. — Alt. 7<.> imn. : long. S] nun.: diameter 24 mm.: uiiibdiiaj angle 87'^. 



This species is (closely allietl to /'. /tii.sfafi/x. but is distinguishable by the ])aucity 

 of its secondary sculpture (such as spines and secondary intercalaries), the nearlv 

 equal prominence of the major and minor riVis in the l(>ft valve, and the ecjuality 

 of the interspaces in the right. (The rilis in tlie rigiit valve of /*. ]iitxf((tii>< occur in 

 pairs, each jiair being separated from those adjacent by spaces perceptibly wider 

 than th(> interspaces between the members of each pair.) The smooth variety 

 of P. hasfiifiix mentioned as occurring in the Pliocene at San Diego. San Gregorio. 

 etc., appears to occupy a position about midway between the typical /'. Ji(ixf((fiis 

 and /*. /ifirxioii. 



The type of /'. hnrxoni. which is now in the collection of the California Academv 

 of Sciences, was collected by Mr. F. M. .\nderson from the I'liocene at the Waldorf 

 asphalt mine, 4 miles south of (iuadaloupe, Santa Barbara County. Mr. Anderson 

 has kindly furnished the following list of fossils from the beds at this mine: Grepi- 

 diila j)riiic<:/ix Conrad, TurrifiUa caoprri C'arpenter. Bitiiuin ((xjieruin Gabb. I'riene 

 orugonennix Redfield, Tr<>rJiif<( coxtelJntd Conrad. Luixdiit liurisii Gould. Xatictt sp., 

 Calliostom.a geminuJatiiui Carpenter, Sada sp., Xasxa perpirujiiix Hinds, Plcurotoma 

 near ('arp''nte}'i((n(t Gahh^ Pli'iimtdina near fri/oniana G&hl), Pf//'ii/<i {'.) ^\y.. Drill ia 

 ^o/v«<f Carpenter, I'l/r/no-i/ i/-i.\pi/fri Chemmtz. Cal luiiMla rii-hthofWii (xabb. Denta- 

 iium sTp., Acniifa up., Panojied (/en'-rosa QtowlA, Led<( tap hr ii t DiiW. Area 'I sp. , Vcn- 

 ericardia ventricosa Gould, Pandont xcaphti Gabli, Tclliiui sp., P>vfcn 2 sp., Murtexia 

 ovoides Gould, Piiacoideif (+ Liu-iim) near (triitiline((ttis Conrad, Phacoidrn sp., 

 Macama sp., Afi/fi/iis sp., Ostrci sp., Echinaravlini ux sp., and coral. 

 , The writer is also indebted to Mr. Anderson for the following list of fossils from 

 a locality 1 mile north of Schumann switch. {?> miles east of the Waldorf asplialt 

 mine), Santa Barbara Countv: Tracliita near viixt,-Untu Conrad, Trochitu near 



