946 DR. H. J. HANSEN ON CRUSTACEANS [Dec.1, 
iv. Synonymical and other Remarks. 
Before proceeding to a systematic arrangement, founded upon 
the characters mentioned, it will perhaps be convenient to under- 
take some reduction of the species, especially of the adult forms, 
with a view to freeing the next chapter, containing notes on the 
structure of the species and their larve, from these disturbing 
investigations. 
The single species established by de Natale, S. arachnipodus 
(p. 19, Tay. ii. fig. 1), is quite unrecognizable to me, and will, in 
my opinion, never be interpreted with certainty; therefore I have 
omitted it from the systematic arrangement. 
_ Of the 15 species described by Kroyer, only 4 (S. frisiz, Kr., 
S. arcticus, Kr., S. cornutus, Kr., S. edwards, Kr.) have been 
established upon adult animals. Bate, Chun, and Ortmann have 
already considered S. frisii, Kr., to be identical with S. atlanticus, 
M.-Edw., but when Bate (op. cit. p. 389) furthermore withdraws 
S. arcticus, Kr., this is, as pointed out by Ortmann, quite wrong. 
Of the remaining 11 species 8 are true Sergestes-larve, while the 
3 others, viz. S. obesus, Kr., S. caudatus, Kr., and S. serrulatus, Kr., 
must be removed from the genus. S. obesus, Kr. (p. 257, tab. iv. 
fig. 10, a—f) is a very curious form ; the single Kréyerian specimen 
had been dissected and most of the pieces are preserved, but an 
investigation of the type specimens of S. sanguineus, Chun (1889), 
proved that this form is identical and that both species have been 
established upon larvee which differ so much from the Mastigopus 
of Sergestes that the species must be removed from this genus, and 
it will be discussed later on under Petalidium, Bate. S. caudatus, Kr. 
(p. 270, tab. v. fig. 14, a—d), is a very young Penwus that has just 
passed the Mysis-stage (Kréyer’s representation of the trunk-legs 
is not correct, as his type specimen possesses a well-developed chela 
on trl.!, behind which pair are found the basal joints of 4 pairs). 
S. serrulatus, Kr. (p. 268, tab. iv. fig. 12, a-g) is a very young 
Acetes, M.-Edw. Finally, S. laciniatus, Kr. (p. 274, tab. v. 
fig. 15, a—c), is, as already pointed out by Ortmann, identical with 
S. corniculum, Kr. 
Of the species described by Stimpson only one is adult, viz. 
S. pacificus, Stimps. (p. 45), and it is, in my opinion, identical with 
S. atlanticus, M.-Edw., as the differences which the author states 
to exist between his species and Kréyer’s description of S. fristi, Kr., 
are of no value. The fact is that the hepatic spine is placed a 
little more behind than in Kréyer’s figure, in which also the 
trunk-legs are delineated a little shorter than they are in the 
animals, Of the other species, S. longicaudatus, Stimps., and 
Sergia remipes, Stimps. (p. 46), can, in my opinion, scarcely be 
recognized without examination of the type specimens. 
Of Serg. meyeri, Metzger (p. 302, tab. vi. fig. 7), I have 
1 T always quote the ‘ Challenger’ Report, not his preliminary paper ; as to 
ag I refer to his monograph, omitting his earlier descriptions without 
eures. 
