1896.] OF THE GHNUS SERGESTES. 963 
third segment is longer than the first or the second by one-half.” 
Unfortunately Faxon does not describe or figure the sixth joint 
of mxp.’ I think that the species wiil prove to be different 
from S. incertus, in. When Faxon states that 6 large pleuro- 
branchiz and one smaller podobranchia are present on each side 
on the body, he certainly has overlooked the 5 lamelle, which I 
have found in S, txcertus and the other species of the edwardsi- 
group. 
S. hamifer, Alc. & And., I will mention here, though I have 
not been able to insert it in my tabular view. The description 
(1894) and the figure (1895) plainly show that it belongs to this 
group. Asin mxp.° “the propus is four-jointed,” the species cannot 
be identical with S. edwards:, Kr., but it is impossible for me to 
settle whether it be really valid or synonymous with one of the 
other species. Only two characters 1 have been able to detect, 
iz.: that mxp.* seems to be still Jonger than in any other species, 
and that its fifth joint is curiously arcuated (see the figure); but it 
is difficult to say whether these two characters are valid, for 
instance, to decide whether the shape of the mentioned fifth joint 
may not be due to some artificial cause. The species must be re- 
examined. 
As mentioned above, I have examined five older Mastigopus- 
forms, four of which have been elsewhere described. The older 
specimens, c. 10-15 mm. in length, are easily recognized from 
each other, and some few characters shall be pointed out; but the 
younger stages are more dificult, being more spiny, &c., and 
besides the materials seen by me are rather insufficient, and the 
animals difficult to characterize without the aid of figures. The 
larve ure easily distinguished from all larve in Group I. by the 
elongated and vigorous mxp.*, and from S. sargassi, Ortm., by the 
longer eye-stalks. In the old larve the sixth joint of mxp.’ is 
divided into 4 subjoints (the oldest Jarval stage of S. oculatus, Kr., 
is unknown to me, so that I cannot settle whether its two distal 
subjoints are divided as in’ S. edwardsi, Kr.), but the armature 
on the end and on the interior margin is very different from that 
in the adults. 
S. oculatus, Kr.—Kroyer has given a good representation (p. 243, 
tab. iii. figs. 5, af); Bate has also described and figured it (p. 406, 
pl. bxxiv. “fic. Alby, Both Kroyer and Bate figure, in my opinion, 
the eye- -stalks a little too long. The rostrum is short, seen from 
the side obliquely triangular, acute, and rather broad at the base ; 
the abdominal segments are dorsally smooth—even in a specimen 
but 6-5 mm. long—and on the ext. br. of urp. the exterior margin 
is ciliated in the total or almost the total length (in a larva 10 mm. 
long, ¢. =, measured with accuracy, of the length was naked). 
By the combination of these three characters the older specimens 
are easily recognized. The species is most decidedly the Mvastz- 
gopus of S. edwardsi, Kr.—S. brachyorrhos, Kr. (p. 272, tab. v. 
tigs. 13, a—b), is the young Mastigopus of S. edwardsi, Kr. I have 
examined Kroyer’s type specimen, which is about 4 mm. long. 
