PETALIFERA. 129 
The number of true species is extremely doubtful, most of those 
described being known by the imperfect original descriptions only. 
A. virescens alone, is well known by Vayssiére’s excellent work on 
the Tectibranchs of the Gulf of Marseilles. 
The name Petalifera was proposed hy Gray as a subdivision under 
Dolabrifera, in 1847; no diagnosis being given. Fischer proposed 
Aplysiella for the same species in 1872, likewise without character- 
ization of the group. 
Subdivisions. 
Petalifera s. str. Shell squarish, with conspicuous posterior sinus ; 
lateral teeth with long cusps. 
Pseudaplysia Pils. Shell oblong-ovate with the sinus obsoiete ; 
lateral teeth with broad, blunt cusps. 

P. VIRESCENS Risso. PI. 36, figs. 9, 10; pl. 55, figs. 10, 11, 12. 
Length 25 to 36 mill. Oval, narrower in front ; surface rough- 
ened by low, tuberculous papille, and sub-epidermal calcareous 
granules under the light spots. Mantle less developed than in 
Tethys, consisting of a nearly hyaline membrane which covers only 
the borders of the shell, most of the dorsal surface of which is ex- 
posed through the large mantle-orifice. | Pleuropodial lobes united 
behind, with thick edges along the short dorsal slit ; foot broad and 
fleshy. ‘Gill milk-white. Genital pore situated a little back of the 
anterior insertion of the pleuropodial lobes. | Genital groove, anus, 
ete. asin Aplysiide generally. 
General color above reddish-brown, or greenish-brown with large 
light spots ; lower surface pale grayish, with only traces of brown 
spots, but with numerous whitish spots due to calcareous particles 
sunken in the tissues. After death the body isa more or less strong 
tint of greenish-yellow. 
Shell squarish, the beak projecting; sinus deeply concave and 
wide. 
Nice (Risso, Robb & v. Beneden) ; Guif of Marseilles (Vayssiére) ; 
lives on floating fucus throughout the Mediterranean (Monts.). 
Aplysia virescente Risso, Hist. Nat. Eur. Mérid., p. 42; A. vires- 
cens t. c., p. 433, pl. 1, f. 10 (1826).— Aplysia petalifera Rana, Hist. 
Nat. Aplys., p. 52, pl. 5, f. 1-8 (1828).—Aplysia unguifera Rane, 
ibid., pl. 5, f. 4-7.—Aplysiella petalifera and unguifera FiscHEr, 
9 
