OCR Text |
Show 1878.] MR. E. J. M1ERS ON THE PENJEID^E. 303 in the female of Peneeus, but is not divided by a median fissure) of the same corneous consistency. All the legs, except the fifth rudimentary pair, are furnished with an exopodite. There is a spine on the under surface of the second joint of the legs of the first three pairs, that on the third pair of legs very small. Hab. Mangalur (Mangalore), west coast of India. Collected by Dr. G. E. Dobson, to whom I have much pleasure in dedicating the species. I have examined four specimens of this species, all of which are certainly females. One of these has been presented by Dr. Dobson to the trustees of the British Museum. The fact that no males have yet been observed renders it possible that the rudimentary and indurated condition of the fifth pair of legs may be peculiar to the female sex-an opinion shared both by Dr. Semper and Mr. Wood- Mason, who have seen the specimens ; and as the mouth-appendages, although presenting some peculiarities, do not depart widely in structure from the type usual in Peneeus, I think it advisable until more specimens shall have been examined, to retain the species in that genus. Should further researches, however, prove that the rudimentary condition of the fifth legs exists in both sexes, the name Mangulura may be adopted to designate the genus, which will be characterized not only by the above-mentioned character, but also by the triangular shape of the terminal joint of the mandibular palpus (which is less delicate and transparent in texture than is usual in Peneeus), and the slender outer maxillipedes. The species will then stand as Mangalura dobsoni1. The form of the fifth pair of legs is not analogous with that characteristic of the very different genus Sergestes, wherein these members, although rudimentary, are very slender, and similar in structure to the preceding pairs. In the form of the rostrum P. dobsoni resembles the Peneeus sculptilis of Heller, from Java (Voy. Novara, Crust, p. 122, pl. xi. fig. 1) ; but, besides the characters derived from the fourth and fifth pairs of legs, which are of the normal form in P. sculptilis, that species differs, if the figure be correct, in the much longer flagella of the antennules, and in the absence of a notch in the posterior margin on the sides of the first and second postabdominal segments, in the form of the first postabdominal segment, which is rounded at its 1 Since writing the above, Professor Wood-Mason has discovered, among specimens of P. dobsoni from the same locality (Mangalore), a single male individual, in which he observed that the fifth legs are fully developed, and which, by his kindness, I a m now enabled to figure (see Pl. XVII. fig. 2, / ) . It is of very small size, not much more than half as large as the females described by me, which it in all respects resembles, except in the fifth legs. These are very slender and elongated, longer, in fact, than those of the preceding pair, with the dactylus much shorter than the preceding joint. The fact, therefore, that the rudimentary condition of the fifth legs is a sexual character peculiar to the female m ay be regarded as definitely established; nor does it seem that this-can possibly be accidental, or due to the loss of the legs and sufcssquent induration of the joint, as the indurated terminal lobe is of the same shape on both legs in all four of the specimens seen by me, and I have never observed a similar condition of the joint in any other specimen of the genus. |