1068 SIR CHARLES ELIOT ON 



50. Chromodorids from the Red Sea^ collected and fiourod 

 by Mr. Cyril Crossland. By Sir Charles Eliot^ 

 K.C.M.G., C.B,, F.Z.S. 



[Received June 12, 1911 : Read June 27, 1911,] 

 (Plate LXI.*) 



The present paper is a pendant to the one preceding it, and 

 gives some account of three species of Chromodoy-is fiom the Red 

 Sea which, though not new, are Worth notice as being either 

 varieties of known species or forms hitherto imperfectly described. 

 The matter which it contains is mainly due to Mr. Crossiand, and 

 I have contributed merely the identification of the species and 

 a few notes on their internal anatomy. The first species, Chr. 

 reticidata, is the one on which Mr, Ci'ossland made his interesting 

 observations regarding the warning coloiation of the genus. My 

 own experience docs not entirely svipport his statement that 

 Chromodorids do not hide under stones but show themselves in 

 the open. I have often found them (as well as Trevelyana crocea) 

 under stones on tropical beaches, where their vivid colours 

 harmonize wonderfully with the ascidians and sponges found in 

 the same locality, so that the nudibranch which when isolated is 

 conspicuous, is almost invisible at home. But, as Mr, Crossiand 

 points out, many species are known to arrive on the shore in 

 considerable bands for the spawning season, and perhaps all do so. 

 At this ci'itical period, at all events, warning coloration must be 

 useful to them. 



The following notes on three Red Sea species indicate that 

 there is considerable variation not only in colour but in the details 

 of the buccal parts. In what appears to be the same species, the 

 denticulation of the teeth and the shape of the elements in the 

 labial armature may vary, and thickenings of the rhachis, 

 a,mounting to rudimentaiy central teeth, may be piesent or 

 absent. 



Chromoeoris reticulata Pease, var. (Pi. LXL figs. 1-3.) 



See Bergh, " Neue Nacktschnecken etc." No. iv.. Jour, Miis. 

 GodefFroy, Heft xiv, p. 9 fi". ; and Eliot, P.Z, S. 1904, pp, 386-7. 



Mr. Crosslaiid's notes on the living animal are as follows : — 



" This sjjecies is of the soft flat kind. Rhinophores with rather 

 high cups. Gills 9, hinder ones short, set in a simple circle open 

 behind, unbranched, simply pinnate, motionless. Foot projects 

 slightly behind the mantle. Mantle-edge slightly or distinctly 

 wavy, according to the extension of the animal. 



" Colour. Greater part of the back a fine network of chocolate- 

 brown on a grey-white ground ; laterally both network and 



* For explanation of tlic Plate see p, 1072, 



