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Show 952 DR. H. J. HANSEN ON CRUSTACEANS [Dec. 1, the 2 branchia? above trl.4 are well developed; the statements of earlier authors on the branchiae of this species are rather deficient. As stated above, 8. ancylops, Kr. (p. 262, tab. iii. fig. 8,a-e), is the Mastigopus of S. atlanticus, and I have seen every stage of transition between the larva and the adult. 8. ovatoculus, Bate (p. 408, pl. lxxiv. fig. 2), is a stage a little older than that described as S. ancylops by Kroyer and Bate. The stages from 7 m m . in length and more are easily distinguished from all other known larvae by tbe shape of the eyes, of which Kroyer has given two good figures, and also in the still younger stages mentioned below the eyes have a rather similar shape; in the older stages the sixth joint of mxp.3 shows the same subdivision into 6 joints as is found in the adult. A small specimen examined by m e is scarcely 6-5 m m . long, trl.4 is even shorter than the two proximal joints of trl.3 together; tbe eyes and the eye-stalks are longer than in the stage figured by Kroyer, reaching a little beyond the basis of the third joint of the antenn. ped.; the first joint of this peduncle is about T\j- longer than the third; the very long aud slender rostrum occupies \ of the length of the eye-stalks and carries a small dorsal spine over its basis ; tbe inferior side of the abdominal segments is without spines, while a rudiment of a spine is present on the dorsal side of the third segment, and tbe spines on the fourth and fifth segments are a little longer than in the following stage; the ciliated part of the ext. br, of urp. occupies a little more than f, but not | of the exterior margin. The smallest specimen examined by m e is but 3-5 m m . long, without the rostrum; the eye-stalks are extremely long, together with the eyes almost as long as the carapace in the median line ; the rostrum reaches almost to the tip of the eyes and is adorned with a shorter dorsal spine at the basis and with some short setae on the distal part ; the supra-orbital and the hepatic spines are considerably elongated. The dorsal spine on the third abdominal segment is rather long, the spines on the fourth and fifth segments very long; the epimera of the 5 anterior segments are each produced into a fine spine bent somewhat outwards ; the spine on the ext. br. of urp. is placed almost before the middle of the exterior margin, and the branch itself is extremely slender, 13 or 14 times longer than broad. This stage, thus rather diverging from the older ones, is, in m y opinion, the youngest Mastigopus, and was taken by Prof. Chun at the Canary Islands. Of S. atlanticus I have seen specimens from the Atlantic, northward to lat. 42° N., from the Indian Ocean and from the Pacific lat. 15° S., long. 109° 20' E., aud the China Sea. S. cornutus, Kr. (p. 249, tab. ii. fig. 2, a-l). This species is easily distinguished from 8. atlanticus, M.-Edw., by the following characters:-The rostrum is much longer, directed obliquely forwards and slenderly acuminated, the eyes are smaller, the third joint of the antenn. ped. is distinctly longer than the first, |
