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Show 960 DR. H. J. HANSEN ON CRUSTACEANS [Dec. 1, 9*6 mm. in length, and the spine is wanting or very small, rarely moderate size. In a specimen 6-2 m m . in length the abdomen has lost its spines, the branchial lamellae to mxp.3 and to trl.'-trl.3 are very large in proportion to the branchia, still being small, and above trl.4 no branchia or lamella is developed. In the older stages the eye-stalks are short aud the eyes are very large, but in the younger stages-between 4-5 m m . and 6*5 m m . in length-tbe eyes are still considerably larger; and in specimens of 4*5-5 m m . in length the rostrum is present as a fine and shorter or longer spine ; and there are short or very short spines on the fourth to sixth abdominal segments. Such a larva, 5 m m . long, is briefly mentioned and figured by Bate (p. 428, pl. lxv. fig. 4) as Mastigopus tenuis, Bate ; tbe figure shows the characteristic process on the fourth joint of mxp.3, the rostrum is not delineated slender enough. The smallest specimen seen by me is, rostrum not included, c. 2-5 m m . long; the rostrum is as long as the carapace in the median line and distally furnished with fine spines ; the eyes are of enormous size and the eye-stalks shorter than in the older stages ; the third abdominal segment has a short dorsal spine, the fourth and fifth segments each a very long, the sixth segment a long dorsal spine. B. For the followdng species, all belonging to the edwardsl-group, I think it convenient to give some introductory remarks, and next to treat the adult animals and the Mastlgopus-iorms separately. Of adult animals there have been described only S. edwardsl, Kr., and S. hamifer, Ale. & And., to which S. halia, Fax., established in 1893, and iu 1895 unjustly withdrawn by the same author, must be added. But in our museum I have found 4 species of adult forms and 5 species of larvae, 4 of which most decidedly belong to the 4 adult forms ; thus an adult form unknown to me"must exist. One of the adult species is S. edivardsi, Kr., but I have not been able to refer any of the three other species to S. India, Fax., or S. hamifer, Ale. & Aud.; the reasons will be given later on. H o w safely I have been able-though not without a rather protracted investigation-to refer the larvae to the adults will appear from the following case. The old larvae are very easy to separate, and I possessed 5 species but only 3 of the adults. By the examination of the characters of the larvae I was induced to re-examine one of the adult species and then it became apparent that it was composed of 2 very closely allied but valid species. Undoubtedly authors have commingled 2-3-4 species in references to S. edwardsl, Kr., and between the limits adopted by Faxon it, as stated above, includes at least 4 species. The adult species are all closely related and very similar to each other. They are all characterized by the above-mentioned powerful development of mxp.3, which is much longer than any of the trunk-legs : the 4 proximal joints are much incrassated and especially tbe thickening of the fourth joint is most conspicuous; the sixth joint is much shorter than the fifth, both strongly compressed and on |
