PLEUROBRANCHUS. 197 



Shell elongated, but little convex, the spire projecting; growth- 

 stride quite apparent; color white (sometimes slightly amber), iri- 

 descent, translucent, calcareous and quite solid. 



Alt. 12, diam. 5 mill. (Vayssiere). 



Gulf of Marseilles ( Vayssiere). 



Pleurobranchus monterosatoi VAYSSIERE, Journ. de Conch., 1880, 

 p. 212, pi. 7, f. 5; Recherches, etc., p. 118, pi. 4, f. 108-112. 

 BERGH, Re's. Camp. Sci. Albert I, fasc. iv, pi. 3, f. 71-74. 



The colors are due to tiny pale ochreous or whitish grains in the 

 integument near the surface, massed together to form the markings. 

 The spire of the shell is longer than in other Mediterranean species. 

 Smaller specimens of the shell measure 5 mill, long, slightly over 2 

 wide ; and the length of the whole animal varies from 30 to 55 

 mill. 



P. PERFORATUS Philippi. PI. 52, figs. 73, 74, 75. 



Body ovate-elliptical, convex ; mantle retuse in front, convex be- 

 hind, obsoletely warty at the sides, and as if perforated all over with 

 numerous deeply impressed points ; foot equalling the mantle ; 

 gill arising at the middle of body, extending nearly to the tip of 

 tail, and adnate for f of its length. Shell large, f the length of 

 body. Length 13, width 8, alt. 6i lines. 



Catania, Sicily. 



P. perforates PHIL., Enum. Moll. Sicil., ii, p. 87, pi. 21, f. 2, (1844). 



Described from an alcoholic specimen which had lost every trace 

 of color. The comparatively large and very thin shell (broken in 

 the type), the adnate gill and punctate mantle, should render it iden- 

 tifiable, although it has not been recognized by later authors. 



P. BREVIFRONS Philippi. PI. 52, figs. 69, 70, 71, 72. 



Mantle ovate, 7 lines long, 5? wide, rounded in front and behind, 

 semiglobose, very smooth. Foot much narrower, but longer than 

 mantle; shell large, thin, oblong, 5? lines long, scarcely over 3 

 wide; gill small. Foot violaceous, verging toward reddish; mantle 

 margin and tentacles sprinkled with violaceous. (Phil.). 



Sicily. 



P. brevifrons PHIL., Enum. Moll. Sicil., ii, p. 87, pi. 20, f. 5, 

 (1844). 



Described from an alcoholic specimen. 



