lOOG.] OF SOUTHERN INDIA AND CEYLON. 639 



The following idontiOcations are probable, but cannot he 

 regarded as certain until further specimoiis are examined : — 



1. Chromodoris fidelis (K.ehi!irt)=i C'hr.Jlanimulata Bei'gh, 



2. Hcjplodoris desmoparypha Bergh = Platydoris papillata 



Eliot. 



3. Astaronotus hemprichi Ehrcnberg = JJoriH exanthemata 



JCelaai-t. 



4. Thord/isa crosslandi Eliot 1904 := JJiaulula (?) (jifjanlea 



Bergh 1905. 



5. Doris int('xta Yib\i)^vt=^Tri'pp)a ornataJi(iY^. 



6. Doris hojjcj/rda K.elaart=7V. monsoni Eliot. 



7. Doridopsis tuberculosa (Q. & G.) viir. = Doris ca/rbv/nculosa 



Kelaart. 



8. Dlphyllidia raarraorata Ke]iif!ii-t= Linguella cinerea Farran. 



9. PhyUohra/nchus orientalis (Kelaart) 



J Ph. prasinus Bergh. 



\ Ph. ruhicundus Bergh. 



In both these ILsts the first name lias priority if the identity is 

 established. 



The following references to genera are certain or probable : — 



1 . (Jhromod^oris (jlev/iei (Kelaart). 



2. C'hr. ? araahilis (Kelaart). 



3. Chr. tennenta'aa (Kelaart). 



4. Platydoris ellioti (A. k H.) ; not Discodoris elUoti. 



5. JlalyerdM ? apnculata (A. & 11.). 



6. Slaurodoris rusticata (A. &l H.). 



7. Doriopjsilla miniata (A. & H.). 



8. Stiliyer ? viridis (Kelaart). 



A specimen marked " Doris osseosa, Ceylon, Dr. Kelaart," 

 appears to be the animal described by me as tS'clerodoris osseosa 

 (Kekart) in Proc. Zool. Soc. 1903, ii. p. 380. 



No one who attempts to determine the species of tropical 

 ISTiidibrarichs can fail to be struck with the great variability 

 of their external characters. Probably no gr-oup of animals offers 

 more striking illustrations of how species arise out of varieties. 

 Even land-slugs show how susceptible the soft moUuscan skin is to 

 changes of colour when it is not protected by a shell ; and in the 

 Nudibranchiata, the watery habitat of which favours the gr'owth 

 of processes and appendages, varijttions of form also are frequent. 

 Again, form, as well as colour, is liable to be distorted by the 

 ordinary methods of presei-vation, and it may happen that two 

 descriptions of the same animal — one treating of the external 

 characters during life, and the other chiefly concerned with the 

 anatomy of a deatl specimen — have nothing in common and are 

 not recognised as referring to the same species. The principal 

 types of structure in the group are now fairly well known ; but it 



Proc. Zool. Soc— 190f3, No. XLIII. 43 



