ISCHNOCHITON. 79 



The type of this species (Mus. Smiths. Inst., 16204) is a pale little 

 Chiton, the color spots being very inconspicuous. The " grating " 

 of the central areas is rather shallow ; the pits are mostly squarish. 

 The posterior denticles of the valves are unequal and irregularly 

 spaced. The girdle-scales have a stony appearance, and only reveal 

 the stripe under strong magnification, and some scales do not show it 

 at all. 



I. CONCINNUS Sowerby. PI. 10, figs. 21, 22. 



Shell oval, wide, subdepressed, most minutely granulated, sub- 

 carinated: valves straight; lateral areas inconspicuous; margin 

 wide, minutely scaly. 



Length one-half, breadth three-eighths inch. (Sowb.*) 



A very neat, small, dark colored species ; granulated, but so 

 minutely as to appear smooth. It is distinctly keeled, yet depressed. 

 The lateral areas are not very distinctly separated from the central. 

 The margin is broad and scaly ; the color dark olive, in some spec- 

 imens nearly black ; inside green. (Soivb.) 



Chonos (Mus. G. B. Sowerby, Sen.) ; Beloncabi (Dr. R. A. Phil- 

 ippi). 



Chiton concinnus SOWB., Charlesworth's Mag. of Nat. Hist. (n. 

 ser.) iv, June, 1840, p. 293 ; Conch. Illustr., f. 117, US.Eadsiella 

 coneinna THIELE, Das Gebiss d. Schn. ii, p. 369, t. 30, f. 19 

 (dentition). 



This form seems to be nearest to I. punctulatissimus Sowb. (vol. 

 xiv, p. 115). I have not seen specimens. 



I. INCA d'Orbigny. Vol. XIV, PI. 27, figs. 52, 53, 54. 



Shell oblong, whitish, depressed, subcarinated ; evenly and very 

 minutely granulated. Length 9 mill. This species is remarkable 

 for its uniform white tint, for its much depressed, subcarinated form, 

 the surface evenly marked with very small points throughout except 

 on the median line, the lateral areas slightly indicated. The margin 

 is very finely scaly. ( Orb.) 



Islay, Peru, in deep water. 



Chiton inca ORB., Voy. dans 1'Amer. Merid., p. 486, t. 65, f. 20- 

 24. 



Probably belongs to the group of Isch. punctulatissimus. The 

 gills are represented as ambient. 



