346 CHITONIDA. 
H. Cryptoidea. 
With double sutural lamine. 
cRYPToconcHus, Guilding. Insertion-plates regular, variable 
behind ; anterior valve with five slits, middle one, posterior irreg- 
ular; teeth very long, smooth; eaves minute; sinus deep, arched ; 
girdle smooth, tufted; valves nearly covered; gills one-third. C. 
porosus. 
AMICULA, Gray.. (Symmetrogephyrus, Midd. Stimpsoniella, 
Cpr.) Shell regular; exposed valves small, mucronate or sub- 
cordate; posterior sutural lamine large; girdle more or less 
pilose, sometimes poriferous. Branchiz median in the typical 
group. C. Pallasii, Midd. (Ixxxvi, 92). 
CHLAMYDOCHITON, Dall. Branchiz encircling. The Amicule 
are provided with pores bearing fasciculi of bristles of a soft or 
horny character, and which, while often irregularly disposed or 
even almost entirely absent (in particular individuals), have a 
tendency to arrange themselves in two rows on each side of the 
median line, one row behind the exposed point of the valve, and 
another near its submerged lateral posterior angle, on each side. 
The mantle is also provided with a coating of fine, chaffy, decid- 
uous scales. C. améeculatus, Pallas (1xxxvi, 93). 
CRYPTOCHITON, Midd, and Gray. Valves entirely immersed. in 
the girdle, which is minutely fasciculately pilose. Branchiz 
encircling. C. Steller, Midd. (Ixxxv, 83).is the largest of the 
Chitons, attaining a length of eight inches...The_ valves. are 
entirely covered, so that ‘their outline even is not indicated in 
fresh specimens, although plainly marked in those which have 
been dried. The Aleutians and Indians eat the foot and. softer 
parts, in the raw state. 
I. Ohitonelloidea. 
Tail-plate funnel-shaped, laminz thrown forward. 
CHITONELLUS, Blainville. 
Insertion-plates very sagittate; slits in anterior valve 5, in 
middle 0-1, in posterior none; teeth very short, except at sutures; 
eaves distinct; sinus very deep and narrow; girdle crowded with 
bristles, no tufts; gills posterior. The species enjoy considerable 
powers of locomotion compared with other groups of the family. 
C. fasciatus, Quoy (Ixxxv, 95). 
CRYPTOPLAX, Gray. Middle valve without slits; girdle with 
crowded bristles, tufted. 
CHONEPLAX, Cpr. Animal creeping, rather long; exposed 
valves small, contiguous; last one infundibuliform; mucro’ 
recurved, terminal ; Jamine as in Katherina, but obsoletely slit ; 
girdle as in Acanthochiton. C. striatus, Sowb. (Ixxxv,'84).9 
CHITONISUS, Cpr. Girdle not poriferous. Based on 0. striatus 
