960 DR. H, J. HANSEN ON CRUSTACEANS { Dee. 1, 
9-6 mm. in length, and the spine is wanting or very small, rarely of 
moderate size. 
Ina specimen 6:2 mm. in length the abdomen has lost its spines, 
the branchial lamelle to mxp.’ and to trl.'-trl.* are very large in pro- 
portion to the branchia, still being small, and above trl.* no branchia 
or lamella is developed. In the older stages the eye-stalks are 
short and the eyes are very large, but in the younger stages—be- 
tween 4-5 mm. and 6°5 mm. in length—the eyes are still consider- 
ably larger; and in specimens of 45-5 mm. 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 mm. long, is briefly mentioned and figured by Bate 
(p. 428, pl. Ixv. fig. 4) as Mastigopus tenuis, Bate; the figure shows 
the characteristic process on the fourth joint of mxp.’*, the rostrum 
is not delineated slender enough. The smallest specimen seen by 
me is, rostrum not included, ¢. 2°56 mm. 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 following species, all belonging to the edwardsi- 
group, I think it convenient to give some introductory remarks, 
and next to treat the adult animals and the Mastigopus-forms 
separately. 
Of adult animals there have been described only S. edwardsi, 
Kr., and S. hamifer, Alc. & And., to which S. halia, Fax., established 
in 1893, and in 1895 unjustly withdrawn by the same author, must 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 larve, 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. edwardsi, Kr., but I have not been 
able to refer any of the three other species to S. halia, Fax., or 
S. hamifer, Ale. & And.; the reasons will be given later on. 
How safely I have been able—though not without a rather pro- 
tracted investigation—to refer the larvee to the adults will appear 
from the following case. The old larve are very easy to separate, 
and I possessed 5 species but only 3 of the adults. By the exa- 
mination of the characters. of the larve 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. edwardsi, 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.*, which is much longer than any of the trunk- 
legs; the 4 proximal joints are much incrassated «nd especially the 
thickening of the fourth joint is most conspicuous; the sixth joint 
is much shorter than the fifth, both strongly compressed and on 
