342 CAUFOUNI.V ACADKMY OK SCIENCES. 



Sul)dass IS01*1>I:IRA. 

 onitT roi.vri.AcoriioRA. 



Superfamily EOCHITONIA. 

 Family LXX.WIII. (JIIITON I D.E. 



Genus Ischnochiton Gntij. 



Shell thin; lamin.f of insertion regular, acute, neither pectinate nor serrate; eaves large; 

 sinus usually smooth; girdle squamose, the squam£e generally striate. 



hchnochiton longicymna Blainv. is a characteristic species. 



403. Ischnochiton regularis Odrpenler. 



Chiton regulan's CPR., Proc. Zool. Soc, 1855, p. 232. 



Ischnochiton regularis Cpr., Keep, West Coast Shells, p. 107, fig. 93, 1S92. Tryon', Man. Conch., 

 Vol. XIV, p. 142, PI. XVII 1, figs. 41, 46, 1892. 



Shell depressed, elongate-oval, width half of length; valves not sharply arched; lateral areas 

 ornamented with concentric, slightly granular ridges and fine radiating lines; central area with 

 inconspicuous fine irregular lines; a])ex smooth; mucro longitudinally ridged with irregular raised lines. 



Description partly from living shell. The only fossil representative of this 

 species so far reported is a perfect central valve found in the upper San Pedro series 

 of San Pedro in 1894 by Dr. G. H. Ashley. 



Living. — Monterey (Carpenter): West Coast (Keep). 



Pleistocene. — San Pedro (Ashley). 



Genus Gryptochiton Midd. <£• Gray. 

 Shell large; valve entirely immerswl in the girdle, which is minutely fasciculately pilose. 

 Type, Cryptochiton stelleri Midd. 



404. Cryptochiton stelleri Middendorff. 



Chiton stcttcri J>Udd., Bull. Acad. St. Peters., Vol. VI, 1846, p. 116. 



Chiton {Cryptochitoii) ste/ieri Midd., Mai. Ross., Pi. i, p. 93, PI. I, figs, i, 2, 1847. 



Chiton amicii/atus Shy . , Thes. Conch., Ill, Chitons, fig. 80. 



Chiton sitkensis Rve., Icon. Conch., PI. X, sp. 55. 



Cryptochiton stelleri Midd., Cpr., Brit. Assn. Rept., 1863, p. 648. Gaisb, Pal. Cal., Vol. II, p. 87, 



1869. Trvon, Struct, and Syst. Conch., Vol. II, p 346, PI. LXXXV, fig. 83, 1883. 



Cooper, 7th Ann. Rept. Cal. St. Min., 18S8, p. 237. Keep, West Coast Shells, p. in, 



fig. 99, 1892. Trvo.v, Man. Conch., Vol. XV, p. 148, PL VII, figs. 7-13; PI. VI, 



fig. 6, 1893. 

 Chiton califomicus Prescott, Am. Jour. Sci., 2nd .Ser., Vol. XXXVIII, 1864, p. 185. 



