966 DR. H. J, HANSEN ON CRUSTACEANS [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 rostrum 
has still essentially the larval shape, with a sharp angle as the 
trace of the dorsal. spine between the oblique basal and the 
horizontal distal part, but the distal part is shorter than the basal 
and its upper margin concave as in the true Mastigopus. 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 adult, 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 3 of the exterior margin, 
and the spine is short. 
S. armatus, Kr.—Kroyer’s representation (p. 260, tab. ii. 
fiz. 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 larve of 
S. incertus, m., and S. penerinki, Bate. In the antenn. ped. the first 
joint is zn the older specimens obviously somewhat 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 2 of the exterior margin, and the spine is well developed. 
The largest specimen is 15°5 mm. long. 
That this Mastigopus 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 ali the 
specimens seen by me were captured in the Atlantic between 
lat. 42° 5’ N. and lat. 4°5' N., but Bate describes and figures 
(p. 401, pl. 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 Islands,” 
and “ between Japan and Honolulu;” thus it may be possible that it 
belongs to S. halia, Fax., captured in lat. 7° 6' N., long. 79° 48' W. 
Of the 8 species enumerated at the end of the tabular view as 
belonging to Group LI., S. hamifer, Alc. & And., S. macrophthalmus, 
Stimps., and S. brachyorrhos, Kr., are mentioned in the notes. The 
other 5 species are all larve. S. diapontius, Bate (p. 399, pl. 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 leng 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. & 
