Vol. XI] BERRY— FOSSIL CHITONS 455 



23. Ischnochiton (Stenoplax) conspicuus (Carpenter, 1879) 

 (Plate VIII, figs. 1-9.) 



1879. Maugerella conspicua Carpenter, in Dall, Proc. U. S. 



Nat. Mus., v. 1, p. 296, pi. 2, f. 11 (radula). 

 1892. Ischnochiton (Stenoplax) conspicuus Pilsbry, Man. 



Conch., (1), v. 14, p. 63, pi. 15, f. 91-96. 

 1914. Ischnochiton conspicuus Oldroyd, Nautilus, v. 28, p. 81 



(recorded from Pleistocene of Signal Hill, Long 



Beach, Cal.). 



1916. Isclmochiton conspicuus Chace, Nautilus, v. 30. p. 71 



(recorded from Pleistocene of Deadman Island. 

 Cal.). 



1917. Ischnochiton conspicuus Chace, Lorquinia, v. 2. p. 30 



(recorded from Pleistocene of Santa Monica, Cal.). 



Diagnosis: Valves moderately heavy, large, depressed or 

 moderately elevated, all but the tail valve slightly concave be- 

 hind, not beaked ; lateral areas strongly elevated, bearing fine, 

 rather wrinkly, radial striae of varying length, those of the 

 terminal areas similar, but finer and often nearly obsolete ; 

 central areas sometimes weakly, longitudinally ribbed, but 

 usually nearly smooth ; head valve slightly everted at apex, its 

 anterior slope strongly concave; tail valve large and flat, with 

 low, central mucro; sutural laminae long, triangular, slightly 

 sinuous; sinus abrupt, deep, of moderate width, with a small 

 notch on each side ; teeth strong and sharp, but surpassed by the 

 massive, projecting, solid eaves ; slit 9 to 12, 2 to 4, 8 to 10. 



Recorded Range: 



Pliocene: San Diego Formation, Pacific Beach, Califor- 

 nia (!). 



Pleistocene: Upper San Pedro Series, Long Wharf 

 Canyon, Santa Monica, California (Chace, !) ; Los Cerritos 

 Hill, Long Beach, California (Oldroyd, !) ; "Coal Mine", 

 west side of Point Loma, San Diego County, California ( !) ; 

 Spanish Bight, San Diego, California ( !). 



Formation doubtful, Deadman Island, San Pedro, Cal- 

 ifornia (Chace, !). 



Indian middens: San Nicolas Island, California (Lowe) ; 

 mouth of Topanga Canyon, near Santa Monica, California 

 ( !) ; Redondo, California ( !) ; La Jolla, California ( !). 



