CLASS GASTROPODA 
271 
rows of prominent pustules which near the girdle project like little cylin¬ 
ders in an irregular manner; interior whitish, with hardly perceptible 
jugal sinuses and very narrow sutural laminae. Length, 7; width, 4; 
height, 1.5 mm. (Dali.) 
Type in United States National Museum, No. 218735. Type locality, 
Pacific Grove, Monterey Bay, California. 
Range. Known only from type locality. 
Ischnochiton brunneus Dali, 1919 
Proceedings of the United States National Museum, 55:504. 
Chiton of moderate size, flattish, of a yellowish brown with a few 
black flecks on the firgle, which is armed with smooth oval slightly imbri¬ 
cating scales; anterior valve with 11, posterior with 14, intermediate with 
single slits; anterior valve with about 16 beaded radial ribs sometimes 
bifurcate, the posterior margin denticulate, the interspaces microscopically 
reticulate; posterior valve flattish, the mucro slightly behind the center, 
with about 14 sometimes bifid rows of pustules with the same reticulate 
ground; the central area is sculptured like the pleural tracts of the inter¬ 
mediate valves; the latter valves have a nearly smooth mucro and feeble 
dorsal carination; the pleural tracts have 8 or 10 axial undulated threads 
on each side, beneath which are more closely set, coarser, transverse 
threads with deeply punctate interstices; the lateral areas have three or 
four radial ribs, the posterior annulate, denticulating the posterior margin, 
the others beaded, the substratum everywhere with the minute reticulation. 
Length, 11 ; width, 12; height, 3 mm. (Dali.) 
Type in United States National Museum, No. 58734a. 1 ype locality, 
San Diego, California. 
Range. Known only from type locality. 
Ischnochiton listrum Dali, 1919 
Proceedings of the United States National Museum, 55:504. 
Chiton of moderate size, straw color, with occasional black blotches 
on the girdle, which is densely minutely scaled ; though the shell is flattish, 
the dorsum is nearly keeled, but the valves are hardly mucronate; the gill 
row lacks one-fourth of being ambient; the anterior valve has about 16 
thread-like, beaded, radial riblets, the two marinal ones are large with half 
a dozen sharp denticles on the edge; the whole shell is covered under its 
stronger sculpture with very minute reticulation; the posterior valve is 
smaller and has 14 riblets like those on the anterior valve; the central 
area is smaller, the mucro being low and behind the center; it is sculptured 
[873 ] 
