MOLLCJSCA OF PLYMOUTH. 453 



only the median indentation^ each tentacle having simply a gently 

 convex or semi-crescentic anterior margin. Thus the young G. cas- 

 tanea approaches G. nodosa in the character of its oral veil, while 

 the young G. nodosa approaches G. castanea in the structure of its 

 lateral folds (pleuropodia) . In both these specimens the transverse 

 ridge usually found on the back was absent ; its place was^ however, 

 indicated in each case by a transverse patch of white pigment. 



The other individuals captured have each been of the full mature 

 size. They were taken under stones between tide-marks, one at a 

 time, at the following localities : — near the bathing pond, April 8th, 

 1890; below the Laboratory, May 17th, — some spawn also under 

 the same stone and on neighbouring ones; in Eum Bay, July 19th, 

 and another a few days later. One of these individuals deposited 

 some spawn in a pie-dish in the form of a double coil, somewhat 

 like that described in my former Report. It is figured on PL XXVII, 

 fig. 3. 



Goniodoris castanea, as Griard^ has already stated, feeds upon 

 compound Ascidians, usually Botryllus ; he found it fairly common 

 at Roscoff in the laminarian zone, and in colour it resembled very 

 often the Botrylli of this zone, upon which it feeds {B. Marionis, 

 B. capucimis, &c.). 



The individual taken in April was on the under side of a stone 

 covered with compound Ascidians, chiefly Botryllus and Botrylloides. 

 It was situated in a fiat patch of gelatinous material which, upon 

 examination, proved to be the remains of a colony of Botryllus, upon 

 which it had evidently been feeding. The colony was quite 

 destroyed, only a few zooids remaining. The red colour of the 

 Nudibranch and its profuse spotting of opaque yellowish white gave 

 it a very perfect resemblance to a colony of a common Botrylloides 

 on the same stone. 



The individual taken on .July 19th was also on the underside of a 

 stone covered largely with flat incrusting colonies of Botryllus. 

 On one of these it was fixed, and had already sucked completely a 

 considerable portion of the colony. Its colours were not in detail 

 those of t. : Botryllus, but Mr. Minchin, who was with me, agreed 

 as to its inconspicuous appearance. 



It should be noticed, however, that Graeffe^ found this species at 

 Trieste " under algae and on hydroid polyps ;" while Herdman^ has 

 dredged two -fine specimens in deep water on different occasions, 

 one off Spanish Head, Isle of Man, the other in Lamlash Bay, Arran. 



1 Giard, Arch. Zool. Exp., ii, 1873, p. 487. 

 * See Bergh, Die Qattung Goniodoris, Malak. Blatt., i, p. 127. 



3 Herdman, First Report on tht Nudibranchiata, Liv. Mar. Biol. Comm. Rep., i, 1886, 

 p. 270; and Notes on the Marine Inv. Fauna, Isle of Man, do., do., p. 319. 



