250 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
depressed lines radiating from the mucro to the inner edges of the pleural 
laminae; lateral areas prominent more or less concentrically rugose; an¬ 
terior valve simple, normal; posterior valve with a conspicuous central 
mucro, behind which it is more or less concave; the whole surface is 
covered with minute, quincuncially arranged pustulation; on the inter¬ 
mediate 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 laminae are short and all the valves 
callous internally, with the points of attachment to muscles and girdle 
impressed; there is no linear arrangement of the pustules on the jugum; 
the ctenidia only reach the seventh valve. Long, of animal about 16; lat., 
6; alt., 3 mm. (Dali.) • 
Type in United States National Museum, No. 109027. Type locality, 
Panama Bay, ‘‘Albatross’’ Station 3393, in 1,020 fathoms. 
Range. Puget Sound, 48 fathoms, to Panama, 1,270 fathoms. 
Lepidopleurus farallonis Dali, 1902 
Proceedings of the United States National Museum, 24:557. 
Chiton small, thin, wide, with a low rounded back and yellowish-white 
color; girdle narrow, sparsely spiculose, with very short, fine, bristly 
spicules; jugum hardly defined, with no obvious mucro; lateral areas 
slightly elevated and feebly concentrically rugose; anterior valve simple; 
posterior conspicuously mucronate and, behind the mucro, concave; sur¬ 
face entirely covered with minute, low, close-set pustules, arranged quin¬ 
cuncially and to some extent concentrically from the mucronal points; 
pleural laminae short, subtriangular; ctenidal line reaching the fifth valve. 
Long, of animal about 10; lat., 5.5; alt., 2 mm. (Dali.) 
Type in United States National Museum, No. 109025. Type locality, 
“Albatross” Station 3104, off Farallon Islands, California, 391 fathoms. 
Range. Farallon Islands, California, to Panama, in deep water. 
Lepidopleurus mesogonus Dali, 1902 
Proceedings of the United States National Museum, 24:555. 
Chiton of moderate size, yellowish or ashy white, with a narrow girdle 
dusted with very minute spicules; valves laterally compressed, almost 
keeled at the jugum, and with the sides meeting there at an angle of 69°, 
slightly rounded at the junction; body narrow, ctenidia about a dozen on 
each side, the most anterior even with the front edge of the seventh plate; 
anterior valve simple, without insertion plates, sculptured with moderately 
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