OPIRTHOBRANCHIATE MOLLUSCA. 33.3 



Family: SCYLL^EID^. 

 Scyllaea pelagica, Linn. 



Amongst the nudibranchs found on the oyster cages which were kept hung over 

 the ship's side from February 15 to March 15, 1903, in the Gulf of Manaar, were 

 two specimens of Scyllcea which agree fairly closely, both in general appearance and 

 also in form of radula and jaws, with S. pelagica. Externally they also rather closely 

 resemble S. marmorata, Ald. and Hanc, from Madras, agreeing with it in the 

 rounded dorsal wings and slight development of the caudal ridge, but it seems to me 

 that there are hardly sufficient grounds for regarding the latter as a distinct species. 



The colouring of the Ceylon specimens, the largest of which measures 3'0 centims., 

 is mainly due to large irregular areas of light-brown stellate chromatophores, amongst 

 which are vacant pale blotches. There are scattered dark spots formed by aggregations 

 of stellate chromatophores which seem to correspond to sub-dermal patches of pigment 

 and also a few small ocellated spots, the centre formed of contracted brown 

 chromatophores, possibly of a different colour during life, and the surrounding paler 

 area of very finely-branched chromatophores. These ocelli occur on the sides and in 

 a row down the centre of the back. 



The body bears a few small colourless tubercles. The buccal mass and, more 

 noticeably, the oesophagus are pigmented with brown stellate chromatophores. 



Family : PLEUEOPHYLL1DIID.E. 



Pleurophyllidia formosa, Kel. Plate I., figs. 14 to 16 ; Plate II., fig. 1. 



One specimen from northern part of the Gulf of Manaar. 



Length of preserved specimen 5 2 centims., width 4 centims., width of foot 

 2 "3 centims. Colour an opaque greyish-brown, paler on the sides of the foot, with 

 remains of black pigment between the dorsal ridges and on the dorsal surfaces of the 

 tentacle shield. 



The form of the animal corresponds closely to the figure given by Bergh (10, 

 plate i., fig. 1). The tentacle shield is broad, with thin projecting upper margin. 

 The back is marked with about 36 slightly raised longitudinal lines, larger and 

 smaller ones irregularly alternating. 



The gill lamellae are about 5 millims. in length, and lie in a crowded transverse 

 band, which runs at about right angles to the direction of the anterior lateral lamellae. 

 The lateral lamellae are numerous, about 50, and run transversely from the body 

 almost to the margin of the mantle, the direction of the anterior ones being somewhat 

 diagonal. 



The jaws (Plate I., fig. 14) are powerful, of a dark horn colour, and of the usual 

 form. The radula (Plate I., figs. 15 and 16) consists of 70 rows of 140-1-140 teeth. 

 The median tooth is very broad (0 - 3 millim. x 0"12 millim.), with four lateral 

 denticles and a strong, rather blunt median point with toothed margins, the basal 



