Vol. XI] BERRY— FOSSIL CHITONS Afl\ 



in all attempts to locate his specimens, and no fossil material 

 of the species is in any of the collections seen by me. From 

 its present range it is a species which one would expect to find 

 in the Lower San Pedro horizons rather than the Upper. Its 

 occurrence in the latter therefore needs confirmation. Arnold 

 did not figure his specimens. 



Subgenus Lepidozona Pilsbry, 1892 



26. Ischnochiton (Lepidozona) pectinulatus Carpenter, 1893* 



(Plate X, figs. 4-6.) 



1864. Lepidopleurus pectinatus Carpenter, Rep. Brit. Assoc. 



Adv. Sci., 1863, p. 649 (not Chiton pectinatus 

 Sowerby, 1840). 



1865. Ischnochiton (Lepidopleurus) pectinatus Carpenter, 



Proc. Cal. Acad. Nat. Sci., (1), v. 3, p. 211. 



1892. Ischnochiton (Ischnochiton) clathratus Pilsbry, Man. 



Conch., (1), v. 14, p. 128 (pars), pi. 26, f. 31-34. 



1893. Lepidopleurus pectinulatus Carpenter, in Pilsbry, Man. 



Conch., (1), v. 14, p. 129. 



Diagnosis 17 : Valves thin, low, carinate; side slopes weakly 

 arcuate; lateral areas elevated, bearing 5-7 closely granose, 

 sometimes bifurcating, radial riblets, the posterior rib lower, 

 but coarser, its tooth-like tubercles projected backward, strongly 

 pectinating the suture ; head valve similarly sculptured, the ribs 

 25-35 in number; sculpture of posterior area of tail valve like- 

 wise similar but a little weaker ; central areas closely and sharply 

 sculptured with 15-19 longitudinal ribs on each side, nearly 

 straight everywhere except on the jugum of the second valve 

 where they strongly diverge, intersected by numerous rather 

 coarser but less sharp transverse bars, the intersections nodular, 

 interstices deeply pitted ; mucro of tail valve low, scarcely pro- 

 jecting, nearly median ; sutural laminae low, arcuate, connected 

 by a dentate plate across the sinus; teeth short and stout; slits 

 11 to 12, 1-1, 14 to 16. 



'"This is Ischnochiton clathratus of many writers on west American chitons, but 

 not, I believe, of Reeve 1847, nor of Chace ( :17, p. 30, = /. sancta-monicce Berry). 

 17 Description drawn in part from recent specimens. 



