952 DR. H. J, HANSEN ON CRUSTACEANS [Dee. 1, 
the 2 branchize above trl.‘ are well developed ; the statements of 
earlier authors on the branchie of this species are rather 
deficient. 
As stated above, S. 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. SS. ovatoculus, Bate 
(p- 408, pl. Ixxiv. fig. 2), is a stage a little older than that 
described as S. ancylops by Kroyer and Bate. 
The stages from 7 mm. in length and more are easily dis- 
tinguished from all other known larve by the 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.’ shows the same 
subdivision into 6 joints as is found in the adult. 
A small specimen examined by me is scarcely 6°5 mm. long, trl.* 
is even shorter than the two proximal joints of trl.’ together ; the 
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 ;1, longer 
than the third; the very long and slender rostrum occupies 2 of 
the length of the eye-stalks and carries a small dorsal spine over 
its basis; the 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 the 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 2, 
but not 3 of the exterior margin. 
The smallest specimen examined by me is but 3°5 mm. 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 sete 
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 my opinion, the youngest Mastigopus, 
and was taken by Prof. Chun at the Canary Islands. 
Of S. atlanticus I have seen specimens from the Atlantic, north- 
ward to lat. 42° N., from the Indian Ocean and from the Pacific 
lat. 15° 8., long. 109° 20’ E., and the China Sea. 
S. cornutus, Kr. (p. 249, tab. ii. fig. 2, a-l). This species is 
easily distinguished from S. 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, 
