556 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.xxiv. 
Dredged by the U. S. Fish Commission steamer AJhafross in the Pa- 
cific, off the Queen Charlotte Islands, British Columl)ia, at station 3342, 
in 1,588 fathoms, ooze, bottom temperature 35. 3*^ F. ; U.S. N. M. , 109019. 
This species is remarkable for the sharp angle made by the planes 
of its valves and for the absence of any regional differentiation of its 
minor sculpture. It is somewhat unusually large for the genus. 
LEPIDOPLEURUS HALISTREPTUS, new species. 
Chiton in general rather similar to the last species and l)est described 
by a differential diagnosis. The girdle is closely and profusely mi- 
nutely spinulose; the scales, being longer and more dense, do not give 
the dusty effect of those of L. 7neso<jonu.s,' the valves are rounded 
above, without well-detined lateral areas or notable concentric rugos- 
ities; their mesial angle is al)Out 104 ; the minute pustulation is 
smaller and rather more prominent; in the posterior valve the mucro 
is depressed and the areas even more feelffy defined; internally the 
valves are callous, the sutural laminre small and subtriangular, the 
lamina? of insertion wholly absent and the girdle attached to a surface 
merely a little rougher than the rest. Lon. of animal al)out 35; lat. 
10; alt. 4.5 mm. 
Dredged b}^ the U. S. Fish Commission steamer Albatross off Aca- 
pulco, Mexico, at station 3415, in 1,879 fathoms, mud, bottom tem- 
perature 36^^ F. (U.S.N.M., 109032), and station 3418, in 660 fathoms, 
bottom temperature 39° F.; U.S.N.M., 109031. 
The rounded back of this species immediately separates it from 
X. mesogonus^ a conclusion which the minor characters confirm. In 
the alcoholic specimen the line of the ctenidia extended forward to the 
anterior edge of the fifth valve. 
LEPIDOPLEURUS LURIDUS, new species. 
Chiton small, solid, narrow, of a lurid smoky color, darker on the 
lateral areas; girdle densely pilose, with whitish spicules; back rounded, 
with the jugum defined feebly, most conspicuous as a distinct mucro, 
mesially, on the intermediate valves; pleural areas divided by obscure 
depressed lines radiating from the mucro to the inner edges of the 
pleural laminav, lateral areas prominent, more or less concentrically 
rugose; anterior valve simple, normal; posterior valve with a con- 
spicuous central mucro, behind which it is more or less concave; the 
whole surface is covered with minute, quincuncially arranged pustu- 
lation; on the intermediate valves the pustules on the lateral and 
pleural areas appear to diverge from the inner margin of the lateral 
areas; internally there is a wide unattached margin on the under side 
of the posterior edge, mesially, in the intermediate valves; the pleural 
lamina? are short and all the valves callous internally, with the points 
of attachment to muscles and girdle impressed; there is no linear 
