TETHYS-ANTILLEAN. 75 



T. MELANOPUS Crouch. PI. 38, figs. 1, 2. 



This form is described as 4* inches long, very plump, foot of a 

 dark brown color ; whole of the body with the exception of the man- 

 tle and foot, is marked with tints of red on the brilliant yellow sur- 

 face. The shell is two inches wide, half-oval, thin, subcartilaginous 

 and marked with faint lines diverging from the straight border ; 

 almost, but not exactly in the middle of the upper portion was a 

 prominence or projection, but so injured as not to be accurately 

 denned. Its surface was slightly tinged with brown. 



East coast of Cornwall. 



Aplysia melanopus CROUCH, P. Z. S., 1870, p. 173, figs. 1, 2. 



Known to me by Crouch's description and figures. The struct- 

 ural characters are still unknown. Type is in British Museum. 



II. Species of the West Atlantic and Gulf of Mexico. 



a. Mantle with a minute median perforation or a little tube ; opa- 

 line gland opening by a single orifice. 

 b. Variegated with rings or ocellated spots. 



c. AVith scattered large black rings, dactylomela, cequorea. 



cc. With many small rings, protea, schrammi. 



bb. Maculated or clouded with blackish ; shell with extremely 



thin calcareous layer, livida, willcoxi, cailleti. 



bbb. Uniform black outside, or nearly so. 



c. Mantle with a tube ; swimming lobes arising far back 



unicolored, braziliana. 



cc. Mantle with perforation ; lobes with spots along inner 



margin, floridemis. 



aa. Mantle with a large median orifice. 



b. Animal small ; shell very convex, calcareous, parvula. 



T. DACTYLOMELA Rang. PL 32, figs. 16, 17, 18, 19. 



Length about 17 cm. Always much swollen, with elongated head 

 and tail ; rugose. Mantle or gill-cover with a minute central tube y 

 and a well developed siphon behind. Swimming lobes not united as 

 far forward as the siphon. 



Color pale yellow of various shades, more or less covered in differ- 

 ent individuals, with black rings, irregular and of various sizes. 

 Inner sides of lobes and the mantle with large black spots of different 

 forms. Borders of the swimming lobes tinged with violet. 



