CLASS GASTROPODA 
259 
some faint and ill-defined brownish spots on the lateral areas, the girdle 
gray. Anterior valve smooth, with some indistinct concentric grooves; the 
anterior slope shorter than the posterior edges; hind margin emarginate. 
Intermediate valves wide and short, with slightly arcuate margins at junc¬ 
tion with girdle, hind margins emarginate. Central areas very minutely 
roughened by diverging wrinkles; lateral areas slightly raised, with a few 
arcuate faint grooves in the direction of growth-lines. Posterior valve 
highest at its anterior margin, the subcentral mucro but slightly projecting, 
the slope behind it about straight. Interior white; valve callus strong; 
sinus concave and shallow, not defined at the edges; sutural laminae but 
little projecting, broadly rounded, invading the sinus. Insertion plates 
hardly longer than the narrowly channelled and solid eavos, sharp and 
smooth. Slits in valve i, 16; valves ii to vii, 1-1 or 2-1 or 2-2, the larger 
number prevailing on the more anterior valves; in valve viii, 13. Posterior 
tooth in the median valves square and well-developed. Girdle rather un¬ 
evenly covered, with convex, pebbly, coarse scales, those toward the outer 
margin elongated, and there is a copious marginal fringe of stout hyaline 
spinules. Gill-row three-fourths of length of foot, with 21 plumes on each 
side. Length, about 14; breadth, 8 mm. (Pilsbry.) 
Type in Academy of Natural Sciences, Philadelphia, No. 69140. Type 
locality, Unalaska. 
Range. Unalaska, Aleutian Islands. 
Described as Trachydermon sharpii Pilsbry. 
Lepidochitona dentiens Gould, 1846 
Proceedings of the Boston Society of Natural History, 2:145. Report of the United 
States Exploring Expedition , Mollusca, 321, fig. 433. 
Testa minima, ovata, carinata, olivacea, ad dorsum albido fulminata, 
omnino minutissime granulata; areis vix distinctis; valvis rostratis postice 
subdenticulatis, dentibus albidis: margo pruinosus. 
Shell minute, ovate, carinate, dark olive, with fine, white zigzag mark¬ 
ings along the back, and dotted black and white along the posterior edge 
of the valves, the white portions seeming to project like minute teeth. 
The whole surface is minutely granulated, and faintly marked by the lines 
of growth. Lateral areas faintly defined, but occasionally marked by a 
dividing line; terminal valves like the others. Margin clothed with hoary 
pubescence. Length, one-fifth of an inch; breadth, three-twentieths of an 
inch. (Gould.) 
Type in United States National Museum. Type locality, Puget Sound, 
Washington. 
[861 ] 
