1918 | Packard: Molluscan Fauna from San Francisco Bay 293 
The valves are covered with a very minute sharp granulation, the granules 
small but well raised, and on the central areas of some specimens they are 
somewhat disposed to be arranged in longitudinal lines converging toward the 
dorsal ridge, this disposition usually stronger toward the lateral extremities of 
the valves. The lateral areas are a little raised, the diagonal lines separating 
them from the central areas rather distinct. The umbo of the posterior valve 
is median, somewhat raised, the slope behind it being depressed and concave. 
The interior is either whitish stained with gray-green or quite green. The 
sutural plates do not project as far as usual, and on some valves they are 
emarginate in front. The jugal sinus is wide, angular, flat or encroached upon 
by the jugum. The anterior valves has 11 slits in the insertion plate, the inter- 
mediate valves 1, the posterior valve has 10 or 12, and some of the median 
teeth are bifid at the tip. 
The girdle is narrow, gravelly, covered with minute scales. 
The gills extend to the front end of the foot.’’ 
Length, 8 mm. 
Occurrence.—At Bonita Point (1). 
Range.—Vancouver Island to San Diego, California. 
Ischnochiton stearnsi Dall 
Ischnochiton stearnsti Dall (1902b), p. 557. 
Description.—This species was originally described by Dall as follows: 
“*Chiton of moderate size, yellowish or buff color; the girdle yellowish white, 
covered with subeylindric, blunt, smooth, close-set, large spines, the ends of 
which have a pebbly appearance, mixed with a smaller proportion of small but 
rather similar spinules; the ends of the large spines, when worn flat, have a 
pavement like aspect; back not heeled, but rather steeply rounded; gills 
ambient; intermediate valves with a dorsal angle of about 90°, the lateral 
areas prominent, with about five radial riblets in each, divaricating to seven 
or ten at the girdle margin, and cut into beads by numerous fine concentric 
furrows; pleural areas and jugum hardly differentiated, sculptured with fine, 
slightly irregular, longitudinal wrinkles, finer mesially; crossed by unconspic- 
ous, less elevated transverse lines; anterior valve with fine, beaded, divaricate 
radial riblets, the insertion plates and eves very short, smooth, not spongy 
with about 17 slits; the posterior valve with a small, low, subcentral mucro, 
from which two elevated lines extend to the margin, one on either side, form- 
ing two areas, and from which the wrinkled sculpture, less prominent on the 
anterior areas, diverges; posterior slits about 15, lateral slits 2, sinus rather 
wide, entire; pleural laminae rather wide and short lon. of animal about 25; 
lat. 15; alt. 6 mm.’’ 
Occurrence.—Dredged by the ‘‘ Albatross’’ off the Farallon Islands 
during a previous survey at station 3104 in 391 fathoms. 
Ischnochiton cooperi Carpenter 
Ischnochiton cooperi Carpenter, Pilsbry (1892-1893), p. 127, pl. 26, figs 
27-30; Wood and Raymond (1891), p. 58. 
Description—The following is Carpenter’s original manuscript description 
of this species as quoted by Pilsbry (1892): 
‘«Shell oval and elevated, with angular dorsal ridge and straight side-slopes. 
