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Show 514 REV. T. R. R. STEBBING ON CRUSTACEANS [May 22, information available. Dana gives a detail-figure of the appendage in question for his E. pellucida and his E. splendens, but it is the latter rather than the former that agrees with the figure delineated by Sars for his E. bidentata. Of Dana's four species, as judged by the figures, it is only superba which has the third joint of the last (developed) leg longer than the fourth. It has been already intimated that the limbs, in spite of their general resemblance, are by no means all of one pattern. It may be added that in the second maxillipeds there is an apical armature which may not be in all species identical. 12. The branchice.-The importance of differences in this apparatus is noticed both by Sars and Dana. 13. First and second pleopods of the male.-Characters derived from these organs appeal chiefly to highly skilled observers, and are not by any means always at their disposal. 14. Uropods and telson.-Characters, perhaps of not overwhelming importance, are derived from the lengths of the two branches of the uropods in relation one to the other and in relation to the telson, from the number and position of spinules on the telson, and from the smoothness or pectination of the telson's subapical processes. So far, then, as at present known, the species will fall into two groups-the first, with the third pleon-segment not produced into a tooth, comprising pellucida, splendens, gracilis, superba, mulleri, bidentata, similis, murrayi, antarctica, latifrons; the second, with the third pleon-segment produced into a tooth, comprising mucronata, gibba, spinifera, gibboides, pseudogibba, schotti, vallentini. each group there are some well-marked species, but others to which the facilities of a synoptic arrangement cannot be very safely applied. Without attempting, therefore, here to formulate such a table, I will only offer some characters by which closely coupled forms may be distinguished one from the other, or by which particular species are distinctly ear-marked. In the first group we observe:- With subquadrate rostral projection E. latifrons Sars. With broadly triangular rostral projection E. antarctica Sars. With very small eyes E. gracilis Dana. ' With two tectb on each lateral margin of carapace E. 'bidentata Sars. E. similis ISars is obviously so named from its supposed likeness to E. bidentata, from which it is distinguished by the unidentate margins of carapace, and inner branch of uropods shorter than outer. Lateral margin of carapace not dentate; uropods reaching beyond telson E. superba Dana. Lateral margin of carapace unidentate ; uropods not reaching beyond telson E. murrayi Sars. In E. pellucida Dana and E. mulleri Claus the inner ramus of the uropods reaches beyond the outer, but not so in E. splendens Dana. In E. pellucida the last three joints of the third parasopod are much shorter than the preceding joint, but not so in E. mulleri. |