384 SIR C. ELIOT ON NUDIBRANCHS [Mar. 1, 



the plumes do not resemble the ample and elaborate rosettes of 

 Archidoris, Platydoris, (fee. The arrangement and the approximate 

 (but not the exact) number of branchiae will probably be found 

 good specific characters in cases where a sufficient number of 

 individuals has been examined ; but I think that the number of 

 pkimes increases with age, at any rate in some species, and that 

 hence the data furnished by a single specimen may be misleading. 

 This is the case particularly in foi-ms with a spiral arrangement, 

 where it seems likely that the small plumes in the spire ai-e 

 developed later than the others. Thus in Chr. syJcesi the number 

 varies from 12 to 18 and in Chr. anmdata from 9 to 16. In the 

 latter species a spire is present in some cases and absent in others. 

 The commonest number of branchise seems to be about 10 

 (varying from 8 to 12 in individuals). A distinctly smaller 

 number (3 to 7) is found in Chr. cardinalis, juvenca, eleganttda, 

 iheringi, krohnii, virginea, gloriosa, sciirra^ luxm^iosa, alhonotata, 

 inconspicua, elegans, camcena, riulolphi, pantharella, and is indi- 

 cated in the di-awings of many other species. In Clir.p)unct%lucens, 

 lineolata, joa^zi^e^'a, tryoni, hennetti, splendens, crossei, dalli, o-eticu- 

 lata, godeffroyana, mollita, vicina, sykesi, and anmdata the number 

 of plumes is more than 12 and often exceeds 20. 



I have observed that in making a superficial examination of the 

 living animal one is very apt to under- estimate the number of 

 branchise, inasmvich as the longer ones may project and the 

 shorter ones be hidden. Hence the plates and descriptions of 

 older authors cannot be considered as decisive on this point. 



6. The labial armature consists sometimes of two plates and 

 .sometimes of a continuous ring. The elements are hardly ever 



straight, but are more or less bent or hooked. They are of very 

 varying shape and thickness, and sometimes swollen just below 

 the tip or terminal hook, so that they assume a mace-like appear- 

 ance. The shape usually afibrds a good specific character, but in 

 some species the elements ai'e bifid in one part of the ai-mature 

 tind entire in another. 



7. The radula ofters many difierences. Chr. scahriuscida has a 

 <3entral tooth and Chr. juvenca a central plate which is called 

 " false " by Bergh, though it seems well developed. Rhachidian 

 thickenings, more or less distinct, are fovmd in Chr. coiridea, 

 iheringi, morchii, gonatophora, porcata, carnea, mariana, hilaris, 

 sannio, lineolata, marenzelleri, cardinalis, reticulata, dalli, cavce, 

 anmdata, splendens. The radula is as a rule of moderate size, 

 but is very narrow in Chr. elegantida, krohnii, gloriosa, and rathei- 

 narrow in pustidans (75 X 28.0.28) and some other forms. In 

 scahriuscida it is 108 x 30.1.30. It is unusually broad in thalas- 

 sopora (71 X 162.0.162), and above all in sijcilla (81x290.0.290). 



The f oi-mulse for the radula given in my descriptions are merely 

 the shortest way of describing the teeth of a given specimen, and 

 must not be understood as necessarily characteristic of the species. 

 The proportion between length and breadth is generally roughly 

 the same in diflrer"ent individuals, but the number of rows and of 



