172 — Remarks on 
foot, with a faint dividing. line running through its 
middle. ^ Mantle tolerably thick, contractile, surrounded 
by numerous short, fibrous processes, as with a fringe, 
which project beyond the shell when the animal is in 
motion, and are endowed with.great sensibility ; on the 
back the mantle is of a deep green color, and exceedingly 
thin and delicate, the. viscera shewing plainly through ; 
it adheres by a strong muscle in its whole extent, save 
at the anterior portion, - where that part covering the 
head and neck floats frée. The head is elongated, 
rounded and terminated by. a. proboscidiform mouth, 
. whose internal edges are furnished with numerous fine 
Lee and the jaws with a thin, pabstripaglar, corneous 
, dings among .the superior viscera, terminating in the 
n» “inferior and posterior portion of the liver. The tentacula,. 
two in number, are long, slender, pointed and contractile, 
inserted about midway on each side of the head, and 
having the eyes black, small but conspicuous, situate 
externally on a slight protuberance at their base. The 
branchial organ arises from the middle of the back of the 
neck, at the bottom of a cavity or open sac, formed by 
that part of the mantle covering the anterior portion of 
.the animal ; the branchis, formed by numerous subtri- 
angular lamella, placed one above the other on =. 
side of-a long, respiratory cordon, and diminishi 
Size toward its termination, always project cds “life 
on the right side of the head, on which side, near their 
origin, are situated the genitalia, the anus opening on 
the same side a little lower down, ; the ovaries are vo- 
