8i 



NUDIBRANCHS FROM THE INDO-PACIFIC. 

 III. 



Bv SIR CHARLES ELIOT. K.C.M.G. 



(No. \., Journal of CoHchohf;}', Oct.. 1905; Ko. II., ditto, April, 1906). 



(Read before the Society, June 12, 1907). 



The present paper contains a description of a new Dorid from 

 Zanzibar, and notes on a small collection of Nudibranchs from 

 Singapore, as well as on living specimens of Doridopsis gefiimacea 

 and Melibe pi/osa, which I was enabled to examine last year at the 

 Biological Station of Misaki in Japan, thanks to the courtesy of 

 Professors Mitsukuri and Ijima. The colour and shape of Nudi- 

 branchs vary so n:iuch and are so often changed or distorted in 

 preserved specimens that no apology is necessary for an account of 

 the external characters as they appear in life. 



The data given here entirely support the idea that as far as 

 Nudibranchs are concerned the whole Indo-Pacific area forms one 

 province. The southern parts of Japan appear to be just on tlie 

 border line. A northern element is visible there, but still several 

 tropical forms extend at least as far north as Yokohama. 



Many of the species described from the IndoPacific are probal)ly 

 mere varieties, but the synonymy of the group cannot be satisfactorily 

 elucidated until we have much ampler records of the limits of varia- 

 bility in the external characters of living animals, and also in sucli 

 internal features as the radula. To some extent the variations 

 appear to be local. Thus, specimens of Chromodoris quadricoloj- 

 {^=Chr. elizabethina) and Chr. ruiici?iata from East Africa show slight 

 but consistent differences from specimens obtained in the Philippines. 

 On the other hand, an inspection of a large number of living speci- 

 mens captured in one locality hardly ever fails to discover considerable 

 variation in coloration and some in shape; so that the tendency to 

 vary is clearly found everywhere and is not merely the result of 

 difference of locality. 



A. — NUDIP.RANCH.S FROM ZANZIBAR. 



Artachaea clavata sp. nov. 



Artiuhrea, Bergh, " Beitriige zur Kenntniss der japanischen Nudi- 

 branchien, II.," Ver/i. k. k. zool. bat. Gesellsch., JJien, vol. 31, 18S1, 

 p. 231, pi. vii., figs. 16-21, viii., figs. 1-6. 



Seven specimens from Kokotoni, Zanzibar, given me by Mr. 

 Voltzkow. The largest is somewhat bent, but measures about 70 mm. 

 in length, and 48 mm. in breadth. The shape is plump, the back 



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