4 
GENERIC CHARACTERS. 
foot above, in common with the entire exposed surface of the body, in- 
cluding the eye peduncles and tentacles, is covered with minute tubercles 
that are arranged in regular rowsf see Plate I, 13, for head and upper 
surface of the body. The body is rather wider than the foot and tapers 
to the quite narrow head. Eye peduncles, Plate 1, 13, ep, are prominent 
but slender and about one third as long as the shell, enlarged terminally 
where there is a prominent eye speck, Plate I, 13, es. The tentacles, 
Plate 1, 13, tt, are'short, not over one third as long as the eye peduncles. 
Mantle, Plate 1, 5, M, large, completely enfolding the body and a portion 
of the foot when the animal withdraws within the shell. All the figures 
on Plate I are greatly enlarged. 
The color of the external portions is pale horn, more or less striped 
with black or dark brown, and occasionally the entire upper portions are 
so colored. 
Upon removing the animal from the shell, the mantle will be found 
to cover the entire surface of the body, quite to the point of the elongated 
abdomen which occupies the interior of the lower five whirls to the tip, 
Plate I, o, a, where the left side of the animal is represented. The man- 
tle is smoother and thinner where it is not exposed than it is on the an- 
terior portions. 
The mouth opens directly beneath the tentacles, Plate 1, 7, 9, 11, o; 
and the entrance, in the contracted animal, is a gullet capable of being 
protruded as far as the jaw, ib., 7, 9, 11, J. This organ is embedded in 
the muscles of the gullet, is crescent shaped, horny, and bright amber 
colored, and the horns of the crescent point downward, thus exposing 
the inner margin which is the cutting edge. There is considerable 
specific variation in the form of the jaw, and some individual, thus on 
Plate I, 1 & 3, 1 have given two jaws of different specimens of Stro- 
phia copia, 3, however, being the usual type. The jaws of all the species 
that I have examined, agree in certain general characters, and appear 
to be made up of two parts, a lower, thicker portion, which becomes 
sharpened into the cutting edge, in the middle of which is a kind of blunt 
tooth, Plate I, 2, z, and a thinner upper portion that edges the lower 
and which is embedded in the muscles, 2, x, where a jaw of S. pannosa 
is represented. Fig. 4 shows a jaw of the smallest species of the genus 
known to me, S. nana, from Little Cayman. The cutting edge of the 
jaw is opposed by the soft, muscular, inner surface of the gullet only. 
The gullet opens just behind the jaw, into a wider, egg shaped 
chamber, Plate I, 7, 8, 9, & 11, s. This organ which is usually called 
the mouth, lies on the back, and a little to the right. Externally, at the 
