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Show 542 REV. T. R. R. STEBBING ON CRUSTACEANS [May 22, very small, and obtusely rounded." In Dana's detail-figure the beak in question is apically emarginate ! 2. Lateral denticles of carapace.-Of these there may be on, or approximate to, each side margin two, or only one, or none. W h e n present they are not easily perceived without separation of the delicate carapace from the body of the animal. They are not mentioned or figured by Dana in a,nj of his four species, but attributed by Sars to three out of those four, Sars finding them in all species except superba Dana and his own antarctica and latifrons; Ortmann also finding them in his three new species described in 1893. Only one species has two denticles on each side, namely, E. bidentata Sars. In E. mulleri Claus gives no clue to their presence. The single denticle is usually near the middle of the margin, but in murrayi Sars it is in front of the middle, and in spinifera Sars behind it. 3. Third segment of pleon with a medio-dorsal backward projection.- This character is common to mucronata, gibba, and spinifera, established by Sars, and to gibboides, pseudogibba, and scliotti, established by Ortmann, and to the new species here described. 4. Length of sixth pleon-segment in relation to that of fifth, or of fifth plus fourth, or of the telson ; the shape of the posterolateral corners of the fifth segment; and the character of the postero-dorsal margin in this and the preceding segment. 5. The compressed ventral tooth at distal end of sixth pleon-segment, called the pre-anal spine.-This is unnoticed by Dana and Claus, but present in all the species described by Sars and Ortmann, except murrayi Sars, superba Dana, mucronata Sars, and schotti Ortmann. It is said to be simple in all the other species except bidentata Sars, in wiiich it is tridentate ; spinifera Sars, in which it is bidentate (as occasionally also in gibba Sars); and pseudogibba Ortmann, in which it is described as 2-4-dentate, rarely simple. In the new species of this paper it is tridentate, at least usually. The variability to which this character seems to be liable is very detrimental to its value. 6. Dimensions of the eyes.-The smallness of the eyes is characteristic only of gracilis Dana and Sars, gibba Sars, and pseudogibba Ortmann. Dana shows it in the figure of his species, without mentioning it in the text. Ortmann, who contrasts small eyes with eyes " tolerably large," makes the comment: " This distinction is apparently dubious; with some practice, however, the size of the eyes in relation to the body is easy to estimate and essentially determines the habitus of the species." One cannot help noticing that between gibboides Ortmann and pseudogibba Ortmann, both occurring in the same localities, there is scarcely any appreciable difference except in the size of the I ody and the size of the eyes. The smaller eyes pertain to the smaller species; and though the inferiority iu the dimensions of the eyes is relative as well as absolute, some suspicion must still attach to the validity of Ortmann's pseudogibba until fuller details are given for separating it from gibboides. |
