NUDIBRANCHIATA. 565 



The body is elongate. The mantle edge is continuous in front : the rhinophores are placed 

 close together: on the neck in front of the rhinophores is a tubercle (caruncula nuchalis) 

 or a series of papillae. Cnidocysts are present. The genera Lingmlla Blv. (= Sancara Bgh.) 

 and Camarga Bergh are closely related and are perhaps only subgenera. 



About 20 species of Pleurophyllidia are recorded from the N. Atlantic, Brazil, Mediter- 

 ranean, Indian Ocean, E. Africa, Malay Ai-chipelago, Polynesia, and California. They generally 

 inhabit mud or sand and their peculiar shape seems correlated with a burrowing habit. I 

 have observed PI. californica in captivity on the West Coast of N. America. It buried 

 itself in the sand with the head and tail exposed and bent upwards, so that the body 

 assumed a crescent-like shape. A continuous current of water was kept passing from the 

 front backwards under the mantle, the edge of which was apparently applied to the sides 

 so as to form a tube over the lamellae. At night however the animals became very lively 

 and moved rapidly round and round the glass dish in which they were confined. 



The species of Pleurophyllidia are more distinct than is common among Nudibranchs. 

 A useful synopsis will be found in von Jhering's paper cited above. They may be divided 

 into the species which have tubercles on the back {PI. pustidosa and marmorata), and the 

 larger number which have longitudinal stripes. This latter class may again be divided into 

 those which have papillae on the neck and those which have merely one more or less well- 

 developed tubercle before the rhinophores. The several species have usually a characteristic 

 dentition. Another point of difference is that some species have numerous separate lamellae 

 at the sides of the body, while others have these lamellae united into three (or in PI. 

 pallida into only one) continuous bands. 



28. PI. gracilis Bgh. 



One mutilated specimen from Minikoi seems referable to this species, which was in- 

 stituted by Bergh for two individuals found at Bombay (S. R. vi. p. 250). There was a 

 large rent which had carried away much of the back, most of the left side and nearly all 

 the internal organs. The length is 2'3 cm. but the body was somewhat bent : the breadth 

 •8 cm. What remained of the dorsal surface was almost colourless, with the remains of 

 numerous yellowish longitudinal bands and occasional traces of brownish pigment. The neck 

 was thickly studded with conical colourless papillae. The gills were fairly numerous and 

 of different sizes. The lamellae on the right side of the body formed three continuous 

 crinkled and sometimes indented lines. The u^apermost extended nearly the whole length 

 of the body : the second was shorter, and the third shorter still. The jaws were strong, 

 the cutting edge armed with numerous rows of minute serrulations. The rhachidian tooth 

 of the radula was as usual squarish : there were 7 — 8 denticles on each side of the central 

 cusp and sometimes two more near its point. The first lateral was also squarish, denticulate 

 on the outer and bearing traces of minute serrulations on the inner edge. The subsequent 

 laterals are denticulate on the outer edge only, and these denticulations decrease as the teeth 

 are further from the centre. The last 10 or 15 teeth are simply hamate and the outermost 

 small and rudimentary. 



It is risky to identify a mutilated specimen, but the essential characters of PI. gracilis 

 seem to be (1) numerous nuchal papillae, (2) small outermost teeth, and the present animal 

 possesses both. 



