550 GASTROPODA. [Opisthobranchia. 



Genus 1. PLEUROBRANCHUS, Cuvier, 1804. 



Pleurobranchus, Cuvier, Ann. du Mus. Hist. Nat., v, 275. Type : P. Peronii, 

 Cuvier. Cleantus, Leach, 1852. 



Body oval ; the mantle about the size of the foot, free, and projecting 

 at the edges all around ; the rhinophores contiguous, inserted below it, 

 above an expansion of the integument or " veil." Gill bipinnate ; male 

 and female generative orifices contiguous or almost united. Jaws com- 

 posed of elongated plates, almost always denticulated on each side of 

 the terminal point. Teeth of radula unciform, sometimes with a small 

 denticle on the inner side of the 3 to 10 first teeth. Shell haliotiform, 

 auriculate, or spatulate, of variable size in proportion to the size of the 

 animal. 



This genus comprises the majority of the species of the family, and 

 is widely distributed. 



Subgen. 1. BERTHELLA, Blainville, 1825. 



Berthella, Blainville, Man. Malacologie, 1825, 469, 627. Type : B. porosa, 

 Blainv. Berthella, Vayssiere, J. de Conch., xliv, 1896, 115. 



Body of animal elongated elliptical and convex ; the mantle de- 

 veloped, margins simple and free ; rhinophores contiguous ; no gland 

 at posterior under-side of the foot. Genital orifices side by side on a 

 common papilla ; verge cylindrical. 



Pieces of the jaws elongated, lozenge-shaped, usually devoid of 

 lateral denticles. Teeth of radula lamelliform, the inner posterior 

 edge denticulated on its upper half. 



Shell auriculate, of medium size. 



Distribtdion. Atlantic, Amboina. Australasia, &c. 



1. Pleurobranchus ornatus, Cheeseman, 1878. Plate 23, figs. 15, a-c; 

 Plate 37, fig. 6. 



Pleurobranchus ornatus, Chsm., P.Z.S., 1878, 275, pi. 15, f. 1, 2 ; T.N.Z.I., 

 xi, 1878 (1879), 378, pi. 16, f. 1. 2 ; M.N.Z.M., 124: Man. Conch. (1), 

 xvi, 206, pi. 47, f. 22, 23 ; Vayssiere, Ann. Sci. Nat,. Zool.. viii, 1898, 

 337, pi. 14, f. 18, 19. 



Animal having the body broadly elliptical, depressed, nearly equally 

 rounded at both ends. Colour varying from pale buff to a clear reddish- 

 brown, with irregularly disposed blotches of a rich dark red-brown. 

 Mantle large, extending over and concealing both head and foot, quite 

 smooth, margin thin, entire. Dorsal tentacles short, stout, abruptly 

 truncate, finely transversely wrinkled, approximate at their origin 

 but gradually diverging at their apices ; colour reddish-brown, tipped 

 with white. Eye-specks black, placed a little distance behind the 

 tentacles, embedded in the integument, but appearing through it. 

 Oral tentacles united in front by a thin semicircular expansion which 

 forms a veil concealing the mouth, and which is carried in advance 

 of the foot. Mouth roundish, with fleshy lips. Branchial plume 

 placed in the groove between the foot and the mantle, large, the pos- 



