Pleurobranchus.] GASTROPODA. 551 



terior third free, composed of about 22 to 24 leaflets. Genital orifices 

 in front of the gill, close together on a single elongated papilla. Verge 

 cylindrical, with a conical sharp point. Foot oblong, pale. There are 

 two jaws on the upper lip ; they are regularly reticulated, the plates 

 lozenge-shaped, with a long and broad median tooth and a tooth- 

 like projection on each side. 



The transverse rows of the radula are meeting at a blunt angle 

 centrally, and bear very numerous unciform teeth with simple cutting- 

 edges, those in the centre and at the margins smaller than the inter- 

 mediate ones. 



Length of animal, 75-100 mm. 



Shell internal, squarish oblong, thin and membranous, semi- 

 transparent, slightly iridescent, closely marked with somewhat irregular 

 concentric striae or folds. Colour varying from nearly white to pale- 

 pinkish or tawny-brown. Spire minute, obscure, the aperture occupy- 

 ing the whole of the ventral surface. Length, 12-20 mm. 



Type. 



Hab. Auckland Harbour, under stones between tide-marks (type) ; 

 Waiwera (T. F. Cheeseman) ; Narrow Neck and Takapuiia (H. S.) ; 

 Maloney's Reef (H. S.). 



Remark. The mandibular plates resemble those of B. gramdata, 

 Kr., figured by Bergh, but the teeth of radula bear no denticles. 



Subgen. 2. BOUVIERIA, Vayssiere, 1896. 



Bouvieria, Vayssiere, J. de Conch., xliv, 1896, 116. Type : Pleurobranchus 

 aurantiacus, Risso. Bouvieria. Vayssiere, Ann. Sci. Nat., Zool., viii, 

 1898, 280. 



Animal ventricose, elliptical ; margins of mantle simple (except 

 in P. scutata), the foot sometimes produced beyond the posterior 

 margin. Gill bipinnate, relatively small. Genital orifices close to- 

 gether, the verge cylindrical, lightly conic at its extremity. Plates of 

 the jaws with several teeth on each side. Teeth of radula unciform. 



Shell auriculate, calcareous, relatively large, and covering the whole 

 of the visceral mass. 



Distribution. Seas of Europe, eastern side of South America, 

 Mauritius, New Zealand. 



2. Pleurobranchus aurantiacus, Risso, 1818. Plate 23, fig. 16. 



Pleurobranchus aurantiacus, Risso, Journ. de Phys. Chim., Hist. Nat., 

 Ixxxvii, 374 ; Hist. Nat. Europe Merid., iv, 1826, 40, pi. 1, f. 8 : Pilsbry, 

 Man. Conch. (1), xvi, 195, pi. 52, f. 76-80 ; pi. 74, f. 97-99 : Vayssiere, 

 Ann. Sci. Nat., Zool., viii, 1898, 281, pi. 13, f. 3; pi. 19, f. 53-55, 58-61 ; 

 pi. 20, f. 75-76 ; pi. 28, f. 186 : Bergh, Reise Philipp., v, 1898, 120, 

 pi. 9, f. 42-47 : Zool. Jahrb. Syst., xiii, 1900, 210, pi. 20, f. 34-38. 

 P. elongatus, Cantraine, Bull. Roy. Soc. Brux., ii, 385. 



Body ovoid. General colour transparent orange, sometimes bright 

 orange or lemon-colour ; tissues very delicate. Mantle small, not 

 covering either buccal veil, rhinophores, or end of the foot. Foot 

 nearly twice as long and as wide as the mantle. Gill pinnate, folded 



