338 CHETONID A. 
looked. by most writers, is also comparable with that of Patella 
vulgata (simultaneously examined and figured), though by no 
means identical. The cephalic ganglia appear to be suppressed, 
forming another evidence of the degeneration or want of develop- 
ment of the cephalic region of this group. 
The above characters are mostly as given by Mr. Wm. H. Dall 
(Proc. Nat. Mus., 1, 283), who has very carefully studied the 
Chitons. He has published an elaborate classification of. the 
group, mainly based upon characters of the valves and their sur- 
rounding girdle—a classification which is largely founded upon 
the studies of the late P. P. Carpenter. I have adopted the 
groups of these eminent naturalists almost throughout, but not 
usually with the values originally assigned to them, believi ing 
that most of their genera had better, at least for the purposes of 
the present work, ‘be considered subgenera. The Chitons are 
constituted an order, Polyplacophora, by Gill, Dall, ete., the 
main character of which is derived from the divided shell; this 
is the principal distinction from the limpets, with which these 
mollusks have many points of analogy. Hubrecht forms for the 
Chitons, etc., a class Amphineura, embracing the orders Soleno- 
gastres and Chitones. 
Curron, Linn. 
Etym.— Chiton, a coat of mail. 
Distr.—More than 250 species are known; they occur in all 
climates throughout the world; most abundant on rocks at low- 
water, but frequently obtained by dredging in 10-25 fathoms. 
Some of the small species range as deep as 100 fathoms. 
North and South America, West Indies, Europe, South Africa, 
Australia, New Zealand, and Sitka. Fossil, 50 sp. Silurian—. 
C. squamosus, Linn. (1xxxv, 57). 
The generic description is equivalent to that of the family. 
Mr. Guilding says of the West Indian species (and his remarks 
will in most particulars apply to others), “‘ They seem to feed 
entirely by night. Though they remain stationary during the 
day, when disturbed they will often creep away with a slow and 
equal pace, often sliding sideways, and creeping under the rocks 
and stones for concealment. If accidentally reversed, they soon 
recover their position by violently contorting and undulating 
. the zone; and for defense they sometimes (when detached) roll 
themselves up like wood-lice. Some of the larger kinds, espe- 
cially of Acanthopleura, are eagerly devoured by the lower orders 
in the West Indies, who have the folly to call them ‘ beef;’ the 
thick fleshy foot is cut away from the animal and swallowed’ 
raw, while the viscera are rejected. We have here a large pale 
Chiton, which is said to be poisonous.” Ladies who are not 
good sailors, and are fond of trying new preventives against 
sea-sickness, may (if: they can) -swallow ‘rdw~Chitons, and 
