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 branchiae, and nudi-brancltiate or naked 

 branchife. The Aplysia belongs to the former, the Doris to the latter. 



APLTSIA DEPILANS The Sea Hare. Plate XXXVII. 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 branchiae, 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 algae. 



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 



