196 PLEUROBRANCHUS. 



Jaws composed of pieces having five denticles on each side of the 

 terminal point (pi. 74, fig. 99). Radula with formula 70.0.70, the 

 lateral teeth with terminal booklet but no denticles below it (fig. 97, 

 group of median teeth ; fig. 98, a large lateral). 



Shell auriculate, the spire a little projecting ; solid, thick but 

 transparent, of a dull amber-yellow color. 



Alt. 11, diam. 7 mill. (Vays.*). 



Nice (Risso), Gulf of Marseilles (Vayssiere) ; Strait between Pico 

 and Fayal, Azores, in 130 meters (Hirondelle). 



Pleurobranchus aurantiacus Risso (Cuvier, Regne Anim., ii, p. 

 396, name only), Journ. de Phys. China., Hist. Nat., Ixxxvii, p. 374 

 (1818); Hist. Nat. Eur. Merid., iv, p. 40, pl.l,f. 8. PniL.,Enum. 

 Moll. Sicil., ii, p. 85, pi. 20, f. 7. GUERIN, Mag. de Zool., 1830, p. 18, 

 pi. 18. VAYSSIERE, Journ. de Conch., 1880, p. 206, pi. 7, f. 1 (shell) ; 

 Recherches, etc., p. 135, f. 102-104 (jaws and teeth).- BERGH, Res. 

 Camp. Sci. Albert I, fasc. iv, p. 26, pi. 3, f. 68-70, 75 ; pi. 4, f. 76- 

 79. MONTS., Nuova Rivista, p. 48. LACAZE-DUTHIERS, Ann. Sci. 

 Nat., xi, 1859, p. 199, pll. 6-12 (anatomy). CANTRAINE, Malac. 

 Medit. et Litt., p. 90, pi. 4, f. 7. P. elongatus CANTRAINE, Bull. 

 Roy. Soc. Brux., ii, p. 385. 



The foot is larger than in P. plumula ; there are fewer denticles 

 on the plates of the jaws. The shell is solid, calcareous, and pro- 

 portionally larger than in any other species except P. membrana- 

 ceus, compared to the size of the animal. It is also distinguished 

 by the deep orange color of the soft parts. 



P. MONTEROSATOI Vayssiere. PI. 52, figs. 66, 67, 68 ; pi. 74, fig. 6. 



Body elliptical, oval, swollen ; general color rosy ochre-yellow. 

 Mantle covering the whole body and emarginate in front, of a deeper 

 ochre tint, with large light spots and numerous ochre-brown or 

 grayish dots. Buccal veil triangular, the two tubular dorsal tenta- 

 cles carried at its base. Foot occupying the entire length of the 

 mantle, but a little narrower than the latter. Gill pinnate, folded 

 longitudinally, quite long and bearing 24 to 25 pinnules on each 

 side. Genital cloaca in front of gill insertion, anus behind. 



Length 55, width 40 mill. 



Jaws composed of chitinous pieces, each with a strong angular 

 denticle, without lateral denticles (fig. 6). Radula with the for- 

 mula 80.0.80 ; lateral teeth all alike in form, with a terminal hook 

 but no denticles below it, as in P. aurantiacus. 



