PLIOCENK PECTKNS. 'i^^ 



Pecten (Pectex) mekhia-MI n. sp. 



PI. XXX, tigs, 1, la, iiTiil -J. 



1900. P,vim ined-ii Merriam (not nf ('.)ijra.l, 1857 = A <->iiirmiis (UnM), Bull. Tal. St. Miii. P.nivan, 

 Xo. 19, 1900, p. •-'•-'2. 



Bi'xcript.ioii.^SlwW averauing ulxnit 115 luilliLiiotors in altitude, loiiocr than 

 hi<;h, iiu'iiuivalve. oquilateral. of medium thicliiie.ss, and with .smooth margins; 

 V)ase. evenly rounded; sides straight or only slightly concave above, sloping at a 

 rather low angle. Right valve decidedly ventricose. with 18 or 19 suhecpial, 

 stroni>-, square ribs, some of which show faint medial sulcations near their 

 extremities; interspaces ilat-bottom(>d and somewhat narrower th;in ribs: whole 

 surface of disk sculptured by more or le.ss iiromineiit lines of growth; hinge line 

 more than one-half length of shell; ears altout (Mpial in length; anterior ear with 

 faint byssal notch, obsolete radiating ridges and tine incr(>ment:d sculpture; pos- 

 terior ear rectangularly truncated, and with faint radial and Hn(> concentric 

 .sculpture. Left valve flat to concave, with a ntore or less prominiMit l>ulge just 

 below the umbo, as in /*. hd/nx; ribs prominent anil rounoed, relati\ely flatter 

 and In-oader as the periphery of the disk is approached; interspaces about as wide 

 as the ribs, round-bottomed, and some of them showing a faint intercalary 

 riblet; surface sculpturinl by flne, sharp, looped, concentric lines; ears ornamented 

 by 5 or 6 rather prominent radiating ridges and mmierous flne concentric lines. 

 Dimenfilonfi. — Alt. 11.5 nun.: long. 130 iimi.; hinge line To mm.; diameter 

 80 nmi. 



/'. ii,erri<(iii.l is distinguishable frotn J'. M/i/s. to which it is allied, by its 

 nuich larger size when adtdt, more numerous ribs (18 to U» in the former, 1-1 to 15 in 

 the latter), relatively longer hinge line (the hinge line of the former being about 

 60 per cent of the length of the disk, while that of the latter is only about 45 

 per cent), and the radial ridging of the ears. 



The types of this species, which are the only .specimens of it so far known, 

 were collected by Mr. Watts from light-colored shale underlying the conglomerate 

 on 8an Felician Creek, near Piru, Ventura County. The following fauna, as 

 given by Doctor Merriam," was associated with P. merriami at the type locality: 

 E<'hhi<ijrichiih(ii near exrcntrlcm^ Macoma near secta^ Nassa sp. indet., Paclnjpoma 

 n. sp., Solen sicarius, and, as determined by the writer, Pecten cerro.wmis. This 

 fauna indicates beds of probable lower Pliocene age. The type of P. merr/'diiu 

 is now in the collection of the California State Mining Bureau, San Francisco. 



Named in honor of Dr. John C. Merriam. professor of paleontology. I'ni- 

 versity of California, to whom paleontologists are indebted for .so much of their 

 knowledge regarding the faunas of the California Tertiary. 



Pliocene (lower). San Felician Creek, near Piru. Ventura County (Watts). 



uBull. Cal. St. Mill. Bureau, Xo. 19, 19UU. pp. ■.■20--i!J. 



