656 SIR C. ELIOT ON NUDIBRANCHS [Juiie 19, 



surmised by Bergh, is identical with Tli. maculigera. Unfor- 

 tunately the buccal parts have been taken out of both the 

 Newcastle specimens, and we must be content with Alder and 

 Hancock's statement : — " Tongue as in D. tuherculata : no collar." 

 This, of course, ought to mean that all the teeth are simply 

 hamate and smooth, whereas in Bergh's Th. maculigera and 

 in my specimen from Zanzibar the outermost teeth bear hair- 

 like denticles. It is probable that there is some variation in 

 this respect, for the shape of the teeth is not exactly similar in 

 my specimen and in Bergh's. Also, after examining Alder and 

 Hancock's two specimens, I am inclined to think that the animal 

 described by me {I. c. p. 368) as Th. stellata is merely a variety of 

 this species. It differs fi'om the typical form in its harder 

 consistency, stellate branchial pocket, and in that the outermost 

 teeth of the I'adula are entire. 



The outermost teeth are found to vary within the limits of the 

 same species in Platydoris argo and Halgerda formosa, being 

 sometimes smooth and sometimes denticulate. 



Thoedisa crosslandi Eliot. 



(Eliot, Proc. Zool. Soc. 1903, ii. p. 368. Cf. Bergh on 

 Diaulula ? gigantea in Siboga-Expeditie, Opisthobranchia, 

 1905, p. 119.) 



After re-examining my specimens, I think this species is 

 identical with the Diaulula gigantea of Bergh. The two de- 

 scriptions are in general agreement and there are some remai-k- 

 able coincidences in details. In both the nervous system is much 

 concentrated ; there is a large prostate, and the penis has a 

 curiously twisted shape, somewhat as in Phialodoris. The 

 dimensions and coloration also agree. There are two points of 

 difference, which perhaps admit of explanation. Firstly, in 

 Th. crosslandi there is a minute, but quite distinct, labial 

 armature, I have found it in all the specimens which I have 

 examined, but it may easily escape notice and may possibly 

 really disappear in some individuals. Bergh found 70 rows of 

 teeth in the radula, and " in den Reihen schienen 150-200 

 Flatten vorzukommen." If this means 150-200 teeth on each 

 side of the rhachis, the radulse in my specimens were smaller and 

 do not exceed 50x110.0.110 as a maximum. Secondly, Bergh 

 describes the dorsal surface as " iiberall fein und dicht granulirt, 

 die Noppchen gerundet, hier und da auch Kegelformig." An 

 inspection of my specimens, confirmed by notes in the living 

 animal (v. Eliot, I. c), shows that the back is covered with 

 elongate pointed papillae, sometimes bearing filaments at their 

 tips. But when preserved in alcohol they often become round 

 owing to contraction and accidental pressure, and sometimes 

 disappear entirely, although in life they are 2-3 mm. long. 



The distinction between the genera Diaulula and Thordisa is 

 perhaps not very clear. Bergh's diagnosis of the former is 

 " Notaeum holosericeum [explained as " sammetartig "J. Dentes 



