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Show 1884.] DURING THE VOYAGE OF H.M.S. 'CHALLENGER.' 333 flattened and not so spine-like as in the last two species; the sixth pair, as usual, are the longest, and project backwards beyond the caudal shield for a space of about its own length; the other epimera increase in size from before backwards ; the anterior and posterior processes by which each epimeron "articulates" with the neighbouring-ones are further away from the proximal end of the epimeron, which gives the epimera the appearance of being shorter than they really are; the fifth and sixth epimera (as well as the three in front) are separated from the tergal portion of the segments by a distinct suture. The epimeron of the first segment shows traces of its original composition out of two epimera by the presence of a transverse ridge, and another ridge, continuous with that upon the cephalic shield, crosses its anterior half, bending backwards at the margin to join the distal extremity of the first transverse ridge; the epimeron of the second free abdominal segment projects for a short distance beyond the caudal shield; the epimeron of the third abdominal segment extends about halfway down the caudal shield. The caudal shield is divided into two portions by a sinuate transverse ridge; it is slightly keeled, and near the anterior margin is a short flat spine in the middle line, on either side of which is an obliquely placed ridge running towards the lateral margin of the caudal shield. The two pairs of antennae are about equal in length. Station 120, 675 fathoms; off Pernambuco. 4. SEROLIS ANTARCTICA, n. sp. The three species just described agree with each other, and differ markedly from all the shallow-water species of Serolis by the enormous development of the epimera; the present species, although an inhabitant of the deep sea, has the general appearance of one of the shallow-water forms. The general form of the body is a broad oval; the epimera are comparatively short, and do not project backwards as long spiniform processes. This species is at once recognizable by the strongly marked sculpturing on the upper surface of the carapace, which is different from that of any other Serolis, and by the entire absence of eyes. In the place of the latter are two minute tubercles about 1 millim. in extent, which show no traces whatever of a faceted cornea, and no nervous structures could be detected beneath the tubercle, the cavity of which is occupied simply by a plug of connective tissue. The sculpturing on the dorsal surface, which is more marked upon the epimera, consists of a number of ridges arranged in a reticulate fashion. The form of the body differs in the two sexes : in the male the outline of the body is more circular than in the female; the breadth of the body ra the former is proportionately greater than the length, owing chiefly to the greater length of the epimera. As in all other species of Serolis the sixth epimera are the longest, and extend just beyond the end of the caudal shield in the male; in the female the terminations of the sixth nair of epimera are just on a level with the end of the caudal shield. The ventral portion of the three free abdominal segments, which P R O C . Z O O L . S o c - 1 8 8 4 , No. XXIII. 23 |