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Show 964 DR. II. J. HANSEN ON CRUSTACEANS [Dec. 1, To his description it may be added that each of the four anterior abdominal segments possesses in tbe median line on the inferior side a protuberance or lobe, the three anterior of these ending in a spine ; on the ext. br. of urp. tbe exterior margin is ciliated in f of its length, thus a very short basal part being naked, but no tooth or spine is present. S. vigilax, Stimps.-The description of Stirapson (p. 45) agrees rather well with the oldest Mastigopus, aud no other species known to me agrees with it; his animals were captured at the Azores. Specimens c. 9-16 mm. in length are distinguished from the related forms by the following characters :-The rostrum about as in S. oculatus, Kr., but perhaps a little larger, directed upwards and forwards; in specimens 9-10 mm. in length the apex is produced into a short spine directed forwards. The eye-stalks are very long, obviously longer than in S. oculatus, Kr.; the eyes large. In the antenn. ped. the first and third joints are of about equal length. The abdominal segments are dorsally smooth, yet in specimens 9-10 m m . long with very short spines or traces of spines on the fourth, fifth, and sixth segments. On the ext. br. of urp. the ciliated part occupies from | (in the younger specimens) to more than A (in the older specimens) of the exterior margin, but the spine is generally obsolete. Tbe adult form is described above, bearing the same name.-As already pointed out by Ortmann, 8. parvidens, Bate (p. 409, pl. lxxiv. fig. 3), 9 m m . long, is established on younger specimens of S. vlgilax, with dorsal spines on the fourth to sixth abdominal segments. Bate's figure gives a rather good idea of this stage. S. macrophthalmus, Stimps. (p. 46), is, in all probability, identical with the stage parvidens, Bate. The smallest specimen seen by me (captured by Chun at the Canaries) is (the rostrum included) 4 m m . long, and differs considerably in several particulars from the older specimens, but is more similar to S. brachgorrhos, Kr. The rostrum is about J as long as the eye-stalks, its short basal part broad, and at its end a dorsal spine, bevond which the rostrum is very slender. The supraocular and the hepatic spines are considerably elongated. The antenn. ped. extremely slender, only 2-jointed, as the second joint is not yet separated from the first; the third is not | of the entire peduncle. Tbe posterior margin of the carapace in the median line with a slender spine directed obliquely forwards (this spine is still preserved in specimens c. 8 m m . long, but then shorter and almost perpendicular). Each of the 6 abdominal segments with a dorsal spine, which is short and perpendicular on the first two segments, longer on the third, fifth, and sixth, very long on the fourth segment. The epimera of the 5 anterior segments produced into a short spine directed outwards ; the same segments besides interiorly in the median line with a lobe, which at least on the second segment is armed with a spine. The very narrow ext. br. of urp. with the exterior margin ciliated in scarcely more than § of its length, and the spine is well developed. The telson very short as in S. brachgorrhos, Kr. |