134 Mr. P. !S. Abraliain an some Genera 



tentacles are united into a thick, fleshy, triantj^ular veil, narrow 

 from before backwards, but laterally extending to the anterior 

 side angles of the foot. To the latter the base of the veil is 

 attached for its whole length, with the exception of a small 

 portion of the extreme pointed ends. The foot is triangular 

 in shape, broad and truncate in front, then gradually nar- 

 rowing to the posterior rounded end, which reaches as far as 

 the hinder mantle-edge. The border is a little expanded and 

 tiatteued. The mouth enters, from below, a chamber with 

 slightly nigose walls, from which leads, anteriorly and above, 

 the constricted opening of a muscular, smooth-walled gizzard, 

 more resembling that of LameUidoris than the homologous 

 arrangement in Acanfhodoris. At the back of the chamber is 

 situated the anterior vertical portion of the narrow odontophore. 

 This organ is without central spines, but is furnished with 

 numerous transverse rows, each containing two bicuspid un- 

 cini or lateral spines (one each side), which are set diagonally. 

 The inner and anterior cusp, in the well-developed tooth, is pro- 

 longed and recurved. The spirit specimens present a pinkish 

 tint on the back, becoming darker and of a violet tinge on the 

 sides and between the tentacles, and shading off into a light 

 brown or flesh-colour, which extends all round the border. 

 The darker tint is due to a minute and close purplish speckling 

 which is seen, under the magnifier, between the papillas, and 

 upon them except at their apices. The dorsal tentacles and the 

 branchiae are opaque yellowish. The under surface is of a 

 uniform flesh-colour. 



Dimensions (in spirit) — length 28 millims., breadth 21, 

 height (or greatest thickness between the pedal and the dorsal 

 surfaces) 10. 



Hab. not stated. The specimens were obtained from the 

 Haslar-Hospital collection. 



The species has been named after Dr. Albert Gunther, to 

 whose courtesy the author is indebted for the opportunity of 

 examining the Nudibranchiate Mollusca in the collection of 

 the British Museum. 



Hexabranchus, Ehrenberg. 



Body more or less depressed, soft ; mantle usually extended 

 laterally and posteriorly, and with undulating border. Dorsal 

 tentacles laminate, kneed, sharply bent, retractile within mar- 

 ginated cavities. Branchi® generally small and numerous, 

 plumose, non-retractile, arranged in six to eight tufts, and set 

 in a circle at some distance around the anal opening. Oral 

 tentacles large, fleshy, ovoid, with crenulate edge. Mouth 



