314 MOLLUSCA. 
inconspicua subterminal: margo latus, filts corners inequalibus mus- 
cosis indulus. 
Chiton muscosus, GouLD; Proceed. Boston. Soc. Nat. Hist., 1. 146. 
July 1846. Expedition Shells, 6. 
SHELL depressed, rather broad-oval, obtusely ridged along the back, 
everywhere sculptured. The colour is pale olive, ashy about beaks, 
and with an ashy-white band along each side of the dorsal ridge. 
Valves large, narrowing towards the sides, so that their edges do not 
come in contact; the lateral valves are small, slightly raised, coarsely 
granulated with square granules arranged in radiating lines; central 
areas deeply incised with sharp, flexuose, but nearly parallel ridges, 
the presenting edges of which are slightly denticulated; these are 
arranged along the back in a plumosely diverging series, and over the 
rest of the spaces they are nearly longitudinal; the spaces intervening 
between the ridges are indented with little alveoli. The anterior 
valve is large and semicircular, having about ten radiating, raised 
lines, and granulated like the lateral areas; posterior valve very small, 
partially umbonated near its extremity, where it is crossed by a faint, 
transverse ridge, nearly parallel with the margin. Margin broad, 
covered with coarse, moss-like, horny fibres or threads, of unequal 
size and length, flexible when wet, very brittle when dry. 
Length two inches; breadth an inch and an eighth. 
Inhabits Puget Sound, Oregon. 
Allied to Ch. brevispinosus, which is much less and very differently 
sculptured, and has stiff, short spines on its margin. The shell figured 
by Mr. Reeve (Conch. Icon., fig. 136), under the name of C. Colliez, 
seems to be the same species; my description was published in May 
1846, a year before that of Mr. Reeve. He says it is the same as C. 
setosus, Sowerby, in Beechey’s Voyage. If so, I should consider the 
first two to be different, as that shell agrees well with a by no means 
rare species from Cape Horn. 
Figure 436, view of the back of the shell. 
