PLEUROBRANCHUS. 195 
Jaws composed of lozenge-shaped pieces, each terminating in a 
single denticle (pl. 74, fig. 96). Radula with the formula 150.0.150, 
the lateral teeth bearing 8 to 10 small denticles immediately below 
the terminal hook (pl. 74, fig. 95). 
Shell haliotiform, quite strong, translucent and iridescent; spire 
little projecting ; color amber yellow; under the microscope a close 
pattern of longitudinal wrinkles is visible (fig. 63) ; these giving the 
iridescent effect. 
Alt. 8, diam. 5 mill.; alt. 7, diam. 4 mill. ( Vayssiére). 
Adriatic and Mediterranean Seas, laminarian and coralline zones ; 
St. Lucie, Cape Verde Is. (Bouvier) ; Strait between Pico and Fayal, 
Azores, 130 meters (Hirondelle). 
Pleurobranchus stellatus Risso, Hist. Nat. Eur. Mérid., iv, p. 41 
(1826).—Rocuepsr., Nouv. Arch. du Mus., 1881, p. 264. 
Pleurobranchus ocellatus DELLE Cu1AJsE, Memorie, Atlas, pl. 104, 
f. 9, 16 (1828). 
P. plumula VayssiERE, Journ. de Conch., 1880, p. 208, pl. 7, f.2 
(shell) ; Rech. Moll. Opistobr., Tectibranches, p. 113, f. 105-107 
(teeth and jaws).—MonrerrosatTo, Journ. de Conch., 1874, p. 281.— 
Bereu, Camp. Sci. Albert I, fase. iv, p. 19, pl. 2, f. 43-50 ; pl. 3, f. 
51-67 ; and ?? Bull. Mus. Comp. Zool. xxv, no. 10, p. 197, pl. 9, f. 
12-14; pl. 10, f. 1-8 (from Lower California! ). Not P. plumula 
Mont. 
Lamellaria kleciacht Brustna, Contr. Faun. Dalm., p. 35 (1866), 
I retain the Mediterranean form separate from that of northern 
Europe mainly on account of the great differences in jaws and den- 
tition. In this species the elements of the jaw have a median point 
but no lateral denticles, and the lateral teeth have numerous short 
denticles below the terminal hooklet. In P. plumuda, as figured by 
Sars, the plates of the jaw are multidenticulate, and the lateral teeth 
apparently lack denticulation. There are also some differences in the 
shells and gills between the two forms. 
The synonymy given is merely tentative. 
P. AURANTIACUS Risso. PI. 52, figs. 76, 77, 78, 79, 80. 
Body ovoid; general color transparent orange, sometimes bright 
orange; tissues very delicate. Mantle small, not covering either 
buecal veii, rhinophores or end of the foot. Foot nearly twice as 
long and as wide as the mantle. Gill pinnate, folded longitudin- 
ally, quite long and with 16 or 17 pinnules on each side. Genital 
orifices and anus as usual in the subgenus. 
Length 31, breadth 17 mill. 
