9G6 DE. n. J. HANSEN ON CIIUSTACEANS [Dec. 1, 



That the referring of this Mastigopus to the above-described 

 adult S. incertus, n. sp., is correct is proved by a specimen c. 17 

 mm. long, which constitutes an excellent transition. The rostrnm 

 has still essentially the larval shape, with a sliarp angle as the 

 trace of the dorsal spine betvi'een the obllfiiie basal and the 

 horizontal distal part, but the distal part is shorter than the basal 

 and its upper margin concave as in the true Mastic/opus. The 

 eyes about as in the adult, but still brown, not black, the eye- 

 stalks as in the adult. The sixth joint of mxp.^ essentially as 

 in the adidt, with 13 spines on the interior margin. The abdo- 

 minal segments are dorsally smooth. On the ext. br. of urp. the 

 ciliated part occupies scarcely more than | of the exterior margin, 

 and the spine is short. 



S. arntatus, Kr. — Kroyer's representation (p. 260, tab. iii. 

 fio-. 6, a-e) gives a good notion of this curious larva. Here I 

 shall but mention some few essential characters. The rostrum is 

 about as long as or a little shorter than the first joint in the 

 antenn. ped., without any dorsal spine or angle. The eye-stalks 

 are of medium length, considerably shorter than in the larvae of 

 S. incertus, m., and S. penerinki. Bate. In the antenn. ped. the first 

 joint is in the older specimens ohviously someivhat shorter than the third. 

 Of the abdominal segments the second is dorsally armed with a 

 shorter perpendicular spine, the third to fifth with very long 

 oblique spines, much longer than in other species of the group, and, 

 besides, the spines on the fourth and fifth segments are much 

 curved. Sometimes a very short spine is present on the first 

 segment, and finally in the younger specimens a short spine on the 

 sixth. On the ext. br. of urp. the ciliated part occupies a little 

 less than f of the exterior margin, and the spine is well developed. 

 The largest specimen is 15-5 mm. long. 



That this Mastiffopus does not belong to S. incertus, m., with 

 which it agrees in the ext. br. of urp., is decided by the shortness 

 of the first joint in the antenn. ped. in proportion to the third. 

 Thus the adult form is unknown to me. Unfortunately all the 

 specimens seen by me were captured in the Atlantic between 

 lat. 42° 5' N. and lat. 4° 5' N., but Bale describes and figures 

 (p. 401, pi. Ixxiii. fig. 1) a specimen, 8 mm. long, which seems to 

 be the same species, and the specimens seen by him were captured 

 at " Port .Jackson (Australia)," "north of the Sandwich Tsiauds," 

 and " between Japan and Honolulu;" thus it may be possible that it 

 belongs to S. hulia. Fax., captured in lat. 7° G' N., long. 70° 48' W. 

 Of the 8 species enumerated at the end of the tabular view as 

 belonging to Group II., S. hamifer. Ale. & And., S. macrophthalmus, 

 Stimps., and S. hrachyorrhos, Kr., are mentioned in the notes. The 

 other 5 species are all larvfe. S. diapontius, Bate (p. 399, pi. Ixxii. 

 fig. 3), is very interesting, being 18 mm. long and easily distin- 

 guished from all other species of the group by having the second 

 joint of the antenn. ped. "twice as long as the first;" this large 

 larva, captured in the Atlantic, must belong to an unknown adult 

 form — thus we obtain at least 7 valid species {S. hamifer, And. & 



