268 GASTEROPODES. 
position, reversed, with the head downwards, are sustained on the suckers 
clothing their tentacular arms. 
Another distinctive denomination is also found among the Gastero- 
podes, into tecto-branchiate or covered branchi@, and n udi-branchiate or naked 
branchia. The Aplysia belongs to the former, the Doris to the latter. 
APLYSIA DEPILANS—The Sea Hare.—Plate XXXVIL. Figs. 1, 2, 3. 
At certain seasons of the year, especially about the middle of sum- 
mer, an animal may be found under the larger stones on the sea-shore, 
bearing much resemblance, in form and habits, to the common naked 
Limax, only exceeding it somewhat when of full size. 
The body is of long triangular shape, extending four inches or more, 
with a distinct head, furnished with four horns, two upright on the neck, 
which may be called cornicula, two terminating the angles of the head, 
tentacula,—a convenient characteristic of each. Nearly between the roots 
of the former are two small black eyes, set in white. A deep cavity in 
the middle of the back, containing the branchive, is surrounded by an 
elevated membrane, with a purple margin closing over it. The sole is 
long and narrow. In certain positions, the head of the animal bears some 
similitude to that of a Doris, particularly from a fold in the higher part 
of the tentacula, not unlike the palpi of that organ. 
The narrowness of the sole indicates that the animal avoids situa- 
tions exposed to the wash of the waves, and that it may frequent the 
region of the more slender zoophytes or alge. 
I took a middle-sized specimen in the beginning of February, but it 
was cramped and contracted by the cold. No race of creatures is more 
readily affected by even a slight degree of refrigeration than all the Lima- 
cine tribe. By heating a glass vessel to receive it, and after replenish- 
ment, by repeatedly dipping it in warm water, the Aplysia was gradu- 
ally restored. . 

It proved a beautiful, fine, and fleshy specimen, of transparent 
chestnut hue, universally strewed with darker specks above, and of dingy 
