380 S[R C. EUOT ox XUmBRAXCHS [Mar. 1, 



[From the Peooeedings of the Zoological Society of London, 



1904, vol. i.] 



[Published August 2, 1904.] 



On some Nudibranchs from East Africa and Zanzibar. 

 Part IV.* By Sir C. Eliot, K.C.M.G., late H.M. Com- 

 missioner for the East African Protectorate, F.Z.S. — 

 Dorididee Cryptobranchiatse, II. 



(Plates XXIII. & XXIV.t) 



[The complete account of the new species described in this communication 

 appears here ; but as the names and preliminary diagnoses were published in the 

 ' Abstract,' such species are distinguished here by being underlined.— Editoe.] 



In my last paper J I discussed the Cryptobranchiate Dorids 



represented by such genera as Archidoris, Discodoris, Platydoris, 



&c. These are oval flattish forms, mostly of sombre coloration, 



with a dorsal surface rarely smooth but generally granulated, or 



bearing papillje, warts, or tubercles. The branchiae are usually 



tripinnate. A labial armature is more often absent than present, 



there is no central tooth, and the radula consists of uniform, 



simply hamate teeth, rarely differentiated or denticulate. In the 



present paper I propose to consider some forms belonging to 



another group typified by Chromodoris and its allies. These 



Dorids are often (but not always) elongated and limaciform in 



shape, brightly coloured, and smooth. The branchiae are usually 



simply pinnate. A labial armature is nearly always present 



(absent only in Thorunna and Aphelodoris). In the radula a 



central tooth is rare, but sometimes occurs (in Cadlina, Tyrinna, 



and Chr. scabi^mscida), and rhachidian thickenings are frequent. 



The teeth ai'e generally denticulate, and the tooth next to the 



rhachis is nearly always different in shape from the others. The 



stomach is usually enclosed in the liver, and there is rarely any 



armature in the reproductive organs. All these characters are 



well seen in Ch'omodoris ; and I am inclined to think that the 



following genera are more or less closely allied to it : — Casella, 



Ceratosoma, Thorumuo, Aphelodoris, Orodoris, Sphcerodoris, 



Cadlina^ Tyrinna, Ealla §, Rostanga, and A^idura. The common 



character possessed by all these forms is in the mouth-parts : 



* For Part III. see P. Z. S. 1903, vol. ii. p. 354. 



t For explanation of the Plates see p. 406. 



X Since writing the third part of this paper {rf. P. Z. S. 1903, vol. ii. p. 854') I have 

 read the last fasciculus by Prof. Bergh which has appeared in Semper's ' Reisen ' 

 (Bd. ix. Th. vi. Lief. i. Nudibranchiata, January 1904), and it appears to me that 

 the n-enus Pernnodnris is practically equivalent to that which 1 proposed to call 

 Sclerodnris, and as it has priority should take the place of the latter name. The 

 only difference in the generic characters is that i'or Peronodoris is given " penis stylo 

 armatus." 1 did not see this style in any of the forms which I have described, but 

 even if it is present in some species and absent in others, this variation would not in 

 my opinion necessitate the creation of separate genera. 



Archidoris violacea Bergh seems nearly allied to my A. africa-iva, and A. nanula 

 Bergh to my A. minor ; but the identity of the forms, thougli not impossible, cannot 

 be demonstrated from the descriptions. 



§ [This name is preoccupied by a Polychaete worm. Hall-a parfhenopeia A. Costa, 

 Ann Acoad. d. Aspiranti Natnralisti Ivapoli, ii. p. 63 (184'tj. — C. Ceosri.amd.j 



