ISCHNOCHITON. 85 



This modest little species is of a dull livid purplish red, with an 

 ashy tinge, especially on the narrow girdle. Except for the well- 

 marked ridges of growth, it appears smooth, but possesses (like all 

 Chitons) a fine reticulation, only visible under a magnifier. The 

 lateral areas are not distinct, the back is very much rounded and 

 the valves well hooked in the median line. The substance of the 

 valves from within appears remarkably spongy as if rotten, or 

 even like vesicular pumice, especially under the eaves. The ante- 

 rior slits are marked by radiating lines of holes, though the teeth 

 between them can hardly be made out. The posterior valve, how- 

 ever, has not this aid to counting, and in the general sponginess it 

 is almost impossible to say how many teeth or denticles exist. It 

 bears no marked resemblance to any other species of the region. 

 (Da//.) 



I. MULTIDENTATUS Carpenter, n. sp. TJnfigured. 



Shell small, reddish-ashen, oblong, vaulted, the jugum very 

 obtuse ; umbo of the last valve submedian ; apices prominent. 

 Entire surface having the appearance of being minutely scaled in 

 quincunx ; lateral areas scarcely distinguishable. 



Interior having 20 slits in the posterior valve, 2 or three in the 

 intermediate valves ; teeth small, solid, obtuse, deeply and broadly 

 separated ; eaves short, spongy ; sinus small, very wide, scarcely 

 laminate. Girdle beset with minute scales. ( Cpr.) 



Bonin Islands (Stiinpson). 



Trachyradsia multidentata CARPENTER, MS. p. 24. 



The type is in the Smithsonian collection. 



The only specimen known^has lost its head valve, and most of the 

 mantle scales; what remain of these, however, are of the Trachy- 

 dermon rather than the Callochiton type. The shell was named 

 Lepidopleurus lepidus by Dr. Gould, but has little in common with 

 that species. There is no character to distinguish it by outside ; 

 but within the incisors are represented by a series of roundish, 

 stumpy, peg-shaped denticles, set rather widely apart in the short 

 spongy gums that are characteristic of Callochiton. The three or 

 four lobes in the side valves are rather longer. (Cpr.') 



I. LINDHOLMI Schrenck. PI. 27, figs. 35, 36, 37, 38, 39. 



Shell ovate, about twice as long as wide, depressed ; olive-green, 

 the eroded umbones rosy-white. Lateral areas and end valves 



