124 THE ATLANTIC. [ CHAP. IL. 
der peculiar circumstances that one can stop the ship in mid- 
ocean and hunt for them, they are little known. One or two 
of their shells are met with in collections; one especially, Ca- 
rinaria, a beautiful little glassy boat, which one would take at 
first for some form of the paper-nautilus. The shell of Caria- 
ria gives no idea, however, of the form of the animal (Fig. 24), 
which, with one or two allied genera—such as Pterotrachea 
and Firoloides, which do not produce shells at all, is sometimes 
abundant in calm weather on the surface of the warm seas. 
Fia. 24.—Carinaria Atlantica. Natural size. Surface. (No. 4.) 
The shell hangs below the animal, connected with it by a kind 
of neck, and is merely meant for the protection of some very 
vital organs, including the heart, the gills, and the liver. The 
remainder of the animal is ten times the size of the shell, and 
forms a large sac, usually gelatinous and very transparent, often 
dotted over with purple pigment spots. The front of the sac 
is drawn out into a long, singularly formed snout, and near it 
there are bright, well-marked eyes and a pair of feelers. The 
posterior part of the sac is produced into a fin-like tail. Along 
the upper middle line of the animal, in the position in which it 
swims in the water, the part corresponding with the “foot” in 
ordinary shell-fish is raised into a high, crest-like fin. The bod- 
ies of these creatures are large, some of them not less than five 
or six inches in length, but, like most free, floating animals, 
