1 1 CALIFORNIA ACADEMY OF SCIENCES. 



28. Pecten (Chlamys) hericeus Gould. 



Plate XI, Fig. 2. 



Pecten hericeus Gld., Proc. Bost. Soc. Nat. Hist., Vol. Ill, 1S50, p. 345; Wilkes E.xpl. E.>;ped., 



Vol. XII, 1852, p. 457, fig. 570. Dall, Trans. Wagner Inst. Sci., Vol. Ill, Part 4, 



1898, p. 708. 

 Pecten hastatus of Carpenter, Brit. Assn. Rept., 1863, p. 645 (not of Sowerby, Thes. Conch., 



1843). ? Gabb, Pal. Cal., Vol. II, 1869, p. 104. ? Cooper, 7th Ann. Rept. Cal. St. 



Min., 1888, p. 257. 



Shell of medium size, triangular ovate, compressed, equivalve, thin; surface of left valve 

 sculptured by about fourteen to sixteen groups of fasciculated ribs, the groups being more prominent 

 and containing more ribs as the middle of the shell is approached; the surface of all the ribs 

 roughened by numerous rather small, erect, arched spines; right valve nearly the same as left; 

 anterior ear of left valve large, acutely pointed with seven to eight sharp, squamosely striated 

 radiating ribs; posterior ear nearly obsolete; ears of right valve the same e.xcept that a deep byssal 

 notch separates anterior ear from disk; sides of umbo rise abruptly from ears. 



Dime^isions. — Long. 40 mm.; alt. 47 mm.; diam. 12 mm.; hinge 19 mm. 



Thi.s species resembles P. hastatus in shape and general characteristics. In 

 P. hastatus there are seven to ten strong, narrow, prominent ribs, coarsely spinose, 

 while in P. hericeus the ribs occur in fourteen to sixteen fasciculi, each fascicle con- 

 sisting of three or four nearly equally prominent, finely spinose ribs, and forming a 

 convex ridge. Specimens identified by Dr. Dall. 



Rare in Pliocene of Deadman Island. The specimen figured is fi-om that 

 horizon and is now in the collection of Delos Arnold. Found rarely in the Pliocene 

 of Pacific Beach, San Diego. 



JAving. — Straits of Fuca (Gould) : ? Sitka to Santa Barbara (Cooper). 



Pleistocene. — San Diego (Dall) : ? Santa Barbara to San Diego (Cooper) : San 

 Pedro (Arnold). 



Pliocene. — San Pedro (Arnold): ? Santa Barbara; San Fernando; San Diego 

 well (Cooper): San Diego (Arnold). 



29. Pecten (Chlamys) hericeus var. strategus Dall. 



Pl.-vte XI, Fig. 5. 

 Pecten hericeus var. strategus Dall, Trans. Wagner Inst. Sci., Vol. Ill, Part 4, 1898, p. 709. 



Shape and general te.xture same as P. hericeus. " The fasciculi of the left valve, to the 

 number of five to seven, with the riblets coalescent, forming large, smooth-backed, turgid ribs, with 

 smaller imbricate intercalary threads. The large ribs sometimes break up suddenly into the usual 

 small riblets near the base. The recent specimens are bright scarlet." (Dall). The right valve oi a 

 young from the Pleistocene of Deadman Island shows nine fasciculi, most of which seem to be made 

 up of two riblets which keep their individuality to the umbo, instead of coalescing; the interspaces 

 are slightly narrower than the fasciculi. The anterior ear of this right valve is prominent and 

 ornamented with six radiating ribs, and near the disk, by elevated lines of growth; byssal notch 

 rather deep; whole surface ornamented with minute, lattice-like scul[)ture. 



Dimensions. — ^Long. 18 mm.; alt. 21 mm.; diam. 5.2 mm.; hinge 9.4 mm. 



