OCR Text |
Show 402 SIR C. ELIOT ox XUDIBRAXCHS [Mar. 1, variable, and does not lend itself to expression in a formula. In most of the larger specimens it is somewhat as follows :- All the branchiae rise from a ring which forms the common support; in front and behind (where it is united with the anal papilla) it is about 4 mm. high. From it rise in front three longish separate plumes, bifid or trifid at the tip. On each side is a group of about five plumes, united together by a common portion some 6 m m . high; each plume is divided into three or four subdivisions, and each of these subdivisions is branched again. The anterior margin of the foot is deeply grooved, but so retracted in most specimens that it is hard to see. The tentacles are also generally retracted. The buccal mass is a large elongated yellow cone, and the retractor muscles are very conspicuous. The labial armature is composed of small slender hooks, rather irregular in shape but not bifid. The large radula is supported by a stiff strong membrane, from which the teeth are not easily detached. In the larger specimens the formula is about 150.0.150 x 70. There is a slight rhachidian fold. The innermost teeth have one denticle on the inner side and 3 to 4 on the outer. The rest bear 1-3 inconspicuous denticles on the outer side only, of which the highest is the largest. The outermost teeth are degraded, but not much serrulated. In one specimen a, number of irregular teeth, bifid and variously jagged, occurred in the middle of several rows. The rest of the internal organs appeared to be as described by Bergh. There is hardly any dilatation which can be called a stomach before the digestive tract enters the liver. Genus SPH/ERODORIS. This genus is characterised by its peculiar dentition, simply pinnate branchiae, and the external conformation of the mouth-parts. In outward appearance the species differ greatly, for whereas punctata, papillata, and verrucosa bear ridges and warts, Iter is is smooth. Bergh classes the genus with Orodoris and Miamira, apparently on account of these warts and ridges ; but it appears to me to be more nearly allied to Chromodoris in virtue of its simple branchiae and its dentition, which is substantially similar, although it has peculiarities of its own. The teeth are straight, long, and thin, with a comb-like denticulation. The innermost are broader than the others and divided into two parts, one of which is smooth and the other denticulate-an arrangement which is perhaps analogous to that of Chr. mbrchii and Chr. gonatophora, where the innermost teeth have one large smooth denticle on the inside and several small ones on the outside, although in Sphcerodoris it would appear that the smooth part of the tooth corresponds to the outside. Four species are known, all from the Indo-Pacific. |