OSCANIU8. 217 



tentacle on each side. The gill consists of 22-24 leaflets ; in front 

 of it is the genital opening, forward of which lies the aperture of the 

 penis, which projects, having a peculiar wing-like expansion on its 

 posterior projecting part. Foot in front and at the sides at least as 

 wide as the mantle, and behind it projects in a blunt angle. Ten- 

 tacles slit down the outer side, cylindrical and hollow. Eyes lying 

 at the base of tentacles, in the slit, so that they may be covered by 

 its free edges. There is a deep incision in the back border of the 

 mantle. 



Shell small, rounded, membranous and transparent, thin, simple 

 and smooth, not composed of layers. 



Living animal, length 5 to 6 inches. In alcohol contracting to 

 3 to 3 inches, 2 to 2J inches broad. 



Massaua W. side of the Red Sea, collected on corals in January 

 (Riippell.). 



Lepus man'mts FORSKAL, Icones rertim naturalium quas in Itinere 

 Orientali depingi curavit Petrus Forskal, p. 9 (name only, referring 

 to) plate 28, fig. A (1776). Pleurobranchus forskalii RUPPELL & 

 LEUCKART, Atlas zu der Reisein N. Afrika, Neue wirbelloseThiere, 

 p. 18, pi. 5. f. 2 (1828). Pleurobranchus ruppellii ISSEL, Malac. 

 Mar Rosso, p. 162 (1869). Not Pleurobranchus forskahli DELLE 

 CHIAGE, Memoire, iii, p. 154 (November, 1828) Oscanius tuber- 

 culatus var. 



Forskal has given a characteristic illustration of this large and 

 peculiar species, although in his posthumous work no description is 

 given. Moreover, he uses the old pre-Linnsean formula ''Lepus mar- 

 inus" for the animal, in his explanation of plates. There is an 

 objection, however, to the use of Riippell and Leuckart's name P. 

 forskali, on account of the fact that it bears even date with Delle 

 Chiaje's similar name for another species. Under these circum- 

 stances I consider that stability of the name will be best conserved 

 by reverting to the earliest, rather than by adopting IssePs proposed 

 change. 



The following form is evidently nearly allied, probably identical. 



O. PURPUREUS Kelaart. Unfigured. 



Deep reddish-purple. Mantle very dark purple, and spotted with 

 still darker purple. There is a bright-white zigzag line on each side 

 of the back of some large specimens. Length nearly 6 inches; 4 



