14 OPISTHOBRANCHIATA OF BRAZIL 



lobe or lobes, rolled to form an excurrent siphon. Genital orifice 

 under front edge of mantle, in front of ctenidium ; hypobranchial 

 gland present, a short distance behind genital opening. Foot 

 well developed. 



Shell very thin, membranaceous, with a thin, calcareous inner 

 layer, nearly as large as mantle, concave, with pointed, small 

 apex, bearing a recurved lamina, and having a concave, posterior 

 sinus. 



This genus is usually known as Aplysia, an etymological 

 correction by Gmelin of the name Laplysia, used by Linne in the 

 1 2th edition of the Systema Naturae. As pointed out by Pilsbry, 

 the name Tethys is unmistakably applied to this genus by Linne 

 himself in the loth edition in 1758, and hence must stand, despite 

 the common but erroneus usage. 



Two species of this genus and one of Notarchus have already 

 been recorded from the coast of Brazil, and to them are to be 

 added the following two, already known from the Antilles. 



Tethys dactylomela (Rang, 1828). 



PL I, Figs. 1-7; PL II, Fig. 8; PL III, Figs. 9-14; PL IX, Fig. 38. 

 Aplysia dactylomela Rang. Histoire Naturelle des Aplysiens, 



1828, p. 56, pi. IX. 

 Tethys dactylomela (Rang). Pilsbry, in Tryon, Manual of 



Conchology, XVI, 1896, p. 75-76, pi. 32, figs, 16-19. 



"Length about 17 cm. Always much swollen with elongated 

 head and tail ; rugose. Mantle or gill cover with a minute, central 

 tube 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 

 different 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. 



"Shell large, much dilated, a little diaphanous, amber colored 

 outside with a visible enamel within; posterior sinus deeply 

 arcuate ; beak recurved, triangular, thick and calloused. Altitude, 

 forty-two millimeters." 



