ELIOT — NUDIBRANCHS. 421 



9. Thordisa crosslandii, Eliot, 1903. (Plate 25. figs. 1, 2.) 

 = Diaulula gigantea, Bergh, 1905. 

 ? = Boris nubilosa. Pease, 1872. 

 See Eliot, in Proc. Zool. Soc. 1906, pp. 656-7, for the identity of these species. 

 One fine specimen from Coetivy. Not dissected. It is somewhat bent, but about 

 12 mm. long and 9 mm. broad. The tips of the rhinophores are dark. The branchia3 are 

 six and greyish. The back is covered with thick-set, soft, conical papilte. The animal 

 was not dissected, in order to preserve it, as being a remarkably fine specimen. I have 

 no doubt that it is the same species as that found by me at Zanzibar and described as 

 Thordisa crosslandii. 



The Doris nubilosa of Pease (American Journal of Conchology, vii. p. 13, 1872) is 

 perhaps the same as this form, but the identity is hardly demonstrable. 



DISCODORIS. 



The lists of this genus contain some species in duplicate under two names and also 

 several doubtful species, both old and new. The examination of a considerable number 

 of type specimens, those of Abraham in the British Museum, those in the collection of 

 the Challenger (British Museum) and of Semper (Copenhagen Museum), and those 

 of Alder and Hancock (Hancock Museum at Newcastle-on-Tyne), enables me, I think, to 

 simplify somewhat the nomenclature. 



Bergh's Disc, concinniformis and Disc. morphcBa are identical with the older D. con- 

 cinna and D. fragilis of A. & H. The D. pardalis of those authors is almost certainly 

 identical with some later species, perhaps with D. cebuensis, but without a better 

 knowledge of the living animals no identity can be proved. Among Bergh's own 

 species an examination of fresh material has convinced me that D. meta is merely a 

 variety of D. boholiensis, and it is also possible that D. cebuensis and D. modesta are 

 yarieties of one form. 



Among Abraham's species the only certain Biscodoris is D. lahifera, redescribed by 

 Mr. Parran. D. vestita is a Diaulula. D. raripilosa is perhaps Bergh's Hoplodoris 

 desmoparypha. D. stragula is not, in my opinion, identifiable. 



The forms from the Atlantic and Mediterranean, where the genus seems well 

 represented, are all fuUy described (though information about the living animals is 

 scanty), but often present some characters at variance with the definition of the genus. 

 I have marked them with a query in the list given below. But I have omitted from 

 this list four species, noticed by Bergh in his description of the Siboga Collection, viz. : 

 D. liturata, D. lutescens, D. versicolor, and J), sibogce. As the author admits, all these 

 forms are extremely doubtful for one reason or another and many of them have features 

 {e. g., the teeth of Disc, lutescens) which are quite anomalous in this genas. They 

 should not, I venture to think, be included in it without renewed examination. 



An examination of the type specimens shows that B. notha (West Indies) and 

 B. concinna (Indo-Pacific) are very nearly allied, but, considering the difi"erence of 

 habitat, I hesitate to identify them without further evidence. 



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