124 ISCHNOCHITON. 



together with the end valves, irregularly, subconcentrically and 

 strongly corrugated. Mucro median, planate. This species is a 

 Stenoplax in form, but a true Ischnochiton in its imbricated scales, 

 which are, however, extremely minute. This specimen is regularly 

 arched, much less elevated than the type, with which, however, it 

 agrees well in particulars. Length 21, breadth 9 mill. (Q>r.) 



I am unable to see why this should not be considered a Stenoplax, 

 unless it be on account of the smaller girdle scales ; but, as I have 

 not seen specimens, I deem it best to leave the species where Car- 

 penter placed it. 



I. SUBCLATHRATUS Pilsbry. Un figured. 



Shell subrotund, depressed (at an angle of 130); brown-olive; 

 valves very wide, the margins lobed, interstices nearly straight. 

 Intermediate valves granulated at the dorsal ridge and more or less 

 all over, having two strongly tuberculate ribs, one diagonal, the 

 other in front of the suture; lateral areas small, granulate; central 

 areas having four longitudinal bars on each side, the bars tuber- 

 culate, interstices granulated. Front valve having about eleven 

 rounded, subtuberculate radiating ribs. Girdle very wide, having 

 close small scales ; valve-margins simple, the anterior having 9 slits. 



Length 4}, breadth 3 alt. '5 mill. 



Mazatlan, under stones. 



Lepidopleurus clathratus CPU., Mazat. Cat., p. 195 (1857) , Ischno- 

 chiton clathratus CPR., MS. Not Ch. clathratus REEVE, Conch. 

 Icon., pi. xviii, f. 113 (1847.) 



I have not seen this species, the name of which has been already 

 used by Reeve. Carpenter writes as follows: 



One very small specimen was discovered on a stone to which a 

 Crucibulum had been attached, beautifully perfect except in the loss 

 of the anterior valve. A dead anterior valve was found of a much 

 larger specimen displaying a marginal structure like that of L. 

 sanguineus. The shell is remarkable for the strong bars across the 

 central areas, and the stout rows of tubercles which run, the one 

 diagonally, the other along the interstitial margin. The mantle is 

 very broad and crowded with minute scales. (C)>r.) 



I have no opportunity of re-examining the type of this minute 

 shell, to see whether the very minute scales are striated. If so, it 

 must closely resemble the young of /. expressus. The paucity of 



