CLASS GASTROPODA 273 
Shell small, subelongate, ashen-colored; much elevated, the jugum 
arcuate. Valves subquadrate, apices concealed, lateral areas little defined, 
having 3-6 rounded, obsolete riblets, here and there with acute projecting 
granules. Central areas pitted all over, interstices small, punctate. Ter¬ 
minal valves with more acute, close, narrow riblets. Mucro little raised, 
anterior. Inside with broad sutural sinus. Insertion plates of intermediate 
valves with one slit on each side, terminal valves with about 12 slits. Girdle 
bearing close, minute scales, which are little elongated. Length, 11; 
breadth, 7 mm. (Pilsbry.) 
Type in United States National Museum. Type locality, Puget Sound. 
Range. Victoria, British Columbia, to San Pedro, California. 
Ischnochiton retiporosus punctatus Whiteaves, 1886 
Transactions of the Royal Society of Canada, 4: Section 4, 1887. 
Shell small, elongated, rather strongly elevated, back distinctly angu- 
lated; color pale-cream or nearly white, but with a few small patches of 
reddish-brown on the girdle and a narrow and noncontinuous series of 
variously interrupted and broken-up yellowish-brown spots upon the me¬ 
dian line of all the valves but the anterior one. Girdle squamose, the scales 
closely imbricating much broader than high, and distinctly striated when 
viewed under an achromatic microscope with half-inch objective. Mucro 
central and tolerably distinct where not worn off; anterior valve marked 
with faint but rather numerous radiating striae and concentric lines of 
growth. Central areas of all the valves but the anterior one regularly pitted 
as viewed by an ordinary simple lens of moderate power, the pitting being 
most distinct near the suture. These pits are the interstices between longi¬ 
tudinal lightly curved and convergent raised lines, and the curved raised 
lines of growth. Lateral areas of the valves (exclusive of the anterior 
one) not so distinctly pitted, but more or less marked with faint radiating 
striae, especially those of the anterior portion of the shell; those of the 
third to the seventh, both inclusive, each bearing from four to six distant, 
isolated, prominent, and rounded tubercles on each side, three being usually 
placed on each of the lines which separate the lateral from the central 
areas. Length, of the only specimen collected, about 14; maximum breadth 
of the same, 6 l /2 mm. (Whiteaves.) 
Type in Ottawa Museum? Type locality, Discovery Passage, at Sta¬ 
tion No. 7. 
Range. Duncan Bay, British Columbia. 
[875 ] 
