OCR Text |
Show 104 SIR C. ELIOT ON NUDIBRANCHS [May 17, divisions, and bears a pair of trifid feathery branchiae, one anteiior and one posterior. The mouth-parts were taken out soon after the specimen was captured, and as preserved consist of a labial armature and radula, but no jaws. It is very likely, however, that the jaws had been lost and were not really absent. The labial armature is much as in B. digitata. Many of the scales are heart-shaped. The formula of the radula is 21 x 9 -J-l-J-9, the number of laterals being constant in all the rows. The median tooth has 7-8 very strong denticles on each side of the central cusp, which does not project much. The laterals are rather short and straight. The second stomach is armed with spines as in B. excepta. The liver sends off diverticula into the process behind the rhinophores and all four pairs of cerata. Those which pass into the rhinophore-sheath and the fourth pair of cerata are simple, while those that pass into the other cerata are divided into four branches corresponding to the divisions of the cerata. The simple tentacles of this animal are a sufficient specific, if not generic character, provided they are normal. It is possible that they are a monstrosity, for it is not uncommon in nudibranchs for external processes to remain undeveloped, for example, I have a specimen of Ceratosoma cornigerum in which the characteristic lobes are wanting. But apart from the tentacles, this specimen does not exactly correspond with B. excepta, for instance as regards the rhinophore-sheaths and radula. The median tooth has fewer and stronger denticulations; the laterals are fewer, shorter, and straighter. P leu ro l eu r a a l b a , sp. n. [Cf. PI. striata van Hass., Eliot in Xudibr. of Maldive and Laccadive Archipelagoes, p. 566-7.] Two specimens from Zanzibar. The following are the notes on the living animal:-" Back white with distinct low ridges, longitudinal but not parallel to median line, each with a yellow line along its summit. The rhinophores stand vertically or point forwards and bear longitudinal perfoliations. The base is white, the main part black, the apex truncated and yellow. They are not retractile into pockets, but can be withdrawn under the mantle-edge. They are not very sensitive. The large velum and the mantle are edged with bright yellow. Foot not half the width of mantle. In crawling, the underside of the mantle is applied to the substratum over which the animal moves. Length 13 millimetres, breadth 4 mm." The dimensions and colour of the preserved specimen have not much altered, though the yellow has become faint. The shape is elongate and tapering. The maximum breadth just behind the rhinophores is 4 millimetres, rapidly decreasing to 3 mm. and 2 mm. One striation runs down the middle of the back ; on each bide of it are six to eight others, not parallel to it and starting |