XUDIBRANCHIATE MOLLTJSCA FROM THE EASTERN SEAS. 135 



velvety. Dorsal tentacles rather large, consisting of a thickish footstalk pointing 

 forwards and a laminated club-shaped portion curving backwards; the whole seated 

 within the rim of a narrow retractile sheath. Branchiae very large, consisting of about 

 seven compound ramified leaflets, radiating from around the anal aperture, and situated 

 near the posterior edge of the mantle. The anterior leaflets (pointing forward), when 

 fully expanded, reach nearly halfway over the back; the posterior leaflets smaller. Each 

 leaflet finely pinnatifid, and the whole forming a beautiful star nearly an inch in dia- 

 meter, concealing the posterior portion of the animal. Foot large, occasionally visible 

 beyond the posterior edge of the mantle ; deeply cleft posteriorly. 



Colour and general appearance. — The whole of the mantle a rich deep velvety blackish 

 brown, edged with fight chestnut. The peduncles of the tentacles blackish, translucent ; 

 the laminated portion like the mantle, and tipped with chestnut ; branchial leaflets 

 dark brown, tipped with light greyish at the edges. Underside of the mantle blackish, 

 translucent ; and foot light brown, shading to chestnut along the margin. 



Two specimens of this handsome Nudibranch were found among rough stones on Slut 

 Island, Haitan Straits, coast of China, near low-water mark, June 30th. 



The animals were sluggish, not moving much, nor fast; they floated readily, foot 

 uppermost, on the surface. The mantle was so capacious that in some attitudes they 

 appeared as broad as long; but when ordinarily crawling, the large and beautiful branchiae, 

 were very conspicuous, occupying nearly the posterior half of the body, and concealing 

 the posterior margin of the mantle and end of the foot, which at that time projects 

 beyond the mantle. 



Messrs. Alder and Hancock * have shown that in the case of Doridopsis nigra there are at 

 least three or more varieties with gradation of tints and markings, and inhabiting the 

 coasts of the Loochoo Islands, Madras, and Ceylon. Our species, D. arborescens, appears 

 quite distinct ; but nevertheless, with such tendency to variation in a form closely related, 

 careful comparison with a series might cause a different view to be taken as to its 

 separation or identity with species already described by other authors. 



Doridopsis rubra, Kelaart. (Plate X. fig. 18.) 



Length 1| inch ; breadth 1 inch. Body thick, sluggish, opalescent. Mantle capacious, 

 thin, covering the whole body, except the posterior portion of the foot ; smooth, semi- 

 transparent, folded posteriorly during progression. Dorsal tentacles pyramidal, short 

 and thick, curved laterally, the footstalks smooth, as long as the upper portions, which 

 are swelled, pointed at the extremities, and laminated. Branchiae consisting of six 

 compound leaflets, like feathers, somewhat unequal in size, surrounding the anus, retrac- 

 tile. Read small, covered with the mantle. Foot left uncovered posteriorly during 

 progression. 



Colour and general appearance. — Mantle of a rich rose-colour, darker in the thicker 

 parts of the back, and paler upon the thinner portions of the sides, marbled on the back 

 Avhen contracted, from corrugation of the surface. Branchiae of the same rose-tint as 



* Ind. Nudib. Moll., Trans. Zool. Soc. vol. v. p. 128. 



