344 NOTES ON SOME BRITISH NUDIBRANCIIS. 



For purposes of comparison I have examined a specimen of A. stelli- 

 fcra, most kindly sent me from Mar.seilles by Professor Vayssiere. It 

 is 31 mm. long, 16 broad, and 10 high, llattish and rather smootli, with 

 low even tubercles. The colour of the dorsal surface is dark olive- 

 brown of various shades ; tlie larger tubercles are yellowish, but the 

 stellate appearance is hardly visible. Tiie under side is pinkish, with 

 reddish brown dots on the lower surface of the mantle. The oral 

 tentacles are longish, conical, and somewhat flattened. The anterior 

 margin of the foot is grooved and perhaps notched, Ijut this is difficult 

 to decide. The edge of the rhinophore pockets is set with small incon- 

 spicuous tubercles. The branchias are eight ; the edge of the pocket is 

 tuberculate, much like the rest of the back, Init has no special tubercles 

 of its own. The formula of the radula is about 18 x 30.0.30 and the 

 shape of the teeth as described above for the Plymouth specimens. 



Neither in this specimen, nor in those from Plymouth, could I find 

 any trace of the armature described by Professor Vayssiere (I.e.) as 

 " anneau chitineux mandibulaire, complet, assez large, offrant dans la 

 partie interne de petits et trus courts batonnets prismatiques." Noth- 

 ing was visible but a thick unarmed cuticle. 



Vayssiere refers this form to Arehidoris, and 1 f(jlluw him ; but if the 

 external teeth are longer and thinner than the internal ones, and if, as 

 Vayssiere has found, a labial armature is sometimes present, it is clear 

 that the division between Arehidoris and Geitodoris is not so sharp as 

 might be supposed. It would be interesting to have statistics as to the 

 uniform presence or absence of the labial armature in various species. 

 There certainly seems to be ground for suspecting that in some species 

 of Arehidoris and Staurodoris it is generally absent, but occasionally 

 present, though not much developed. With reference to this and many 

 other organs, we have little information as to the effect of age and 

 growth on the external and internal characters of Nudil)ranchs. 



GEITODORIS PLANATA (A. & H.). 



(Alder and Hancock, Monograph, Plate VIII., and Part VII. p. 42. Eliot, 

 Proc. Mai. Society of Loudon, Sept., 1904, vol. vi. No. 3, pp. 180-1.) 



In the paper cited above I have described specimens caught at 

 Plymouth, and considered in the Laboratory to be D. planata, 

 A. & H., and have also given my reasons for referring them to Geito- 

 doris. Since writing this 1 have examined two other preserved specimens 

 at Plymouth. The back is granulate, with some larger tubercles, and 

 also with some pits, which often give the u])per side a honeycombed 

 appearance. The mantle edge is broad, and on tiie under side veined 

 with anastomosing lines. The branchiae appear to be nine, and in small 



