56 DR. H, J. HANSEN ON CRUSTACEANS [Jan. 20, 
described ; the posterior branchie to a large degree are destroyed, 
and as to the other features, I refer to Bate’s description (p. 429). 
I cannot say with certainty whether the animal is a very young 
specimen of P. foliacewm Bate, or belongs toan unknown form; the 
rostrum deviates considerably from the type of P. foliacewm, but 
its shape presents a stage between those in the adult and im a larva, 
nearly agreeing with that in a larval form mentioned below. 
In my earlier paper on Sergestes I described S. obesus Kr. 
(=S. sanguineus Chun). I stated that it was a larva, a Masti- 
gopus, and added (p. 968): ‘It is easily seen that this species 
cannot remain in the genus Sergestes, but whether it should be 
referred to Petalidium Bate, or a new genus should be established 
for its reception, is impossible to decide with certainty. The 
branchial plates recall the plates found in Petalidiwm, and there- 
fore I provisionally transfer it to that genus....” I had not 
seen any adult Petalidiwm, but suggested (p. 967) that the 
branchial plumes interpreted by Bate as arthrobranchie are in 
reality pleurobranchie. I can now decide that S. obesus Kr. is 
the Mastigopus of Petalidiwm: the branchie prove it; besides, 
trl.2 in the Mastigopus is exceedingly elongate, with the basal 
part very thick, and in the adult form the basal joint of the same 
pair (fig. Le) is exceedingly thick, very much thicker than those 
of trl.) and trl.?. Finally, the shape of the rostrum of S. obesus 
Kr. agrees nearly with that of the young Petalidiwm from 
Stat. 137 just mentioned. I described the branchiz of S. obesus 
Kr., stating that in the largest specimen a rudimentary branchia 
was found above trl.*; in the largest but one of the specimens I 
have now looked for this branchia, and foundit. Finally, I stated 
that P. obesum (Kr.) is “decidedly distinct from P. foliaceum Bate,” 
and I maintain this opinion, founding it on the fact that P. foli- 
aceum does not possess any branchia above trl.*; and it is very 
improbable that such a branchia begins to develop itself in the 
Mastigopus and disappears again in the adult. 
6. Sereestes H. M.-Edw. 
SERG. INTERMEDIUS Bate, p. 383 (no figure). 
Bate mentions one specimen, 5 mm. in length, from the 
“China Sea, off Luzon.” The specimen has been preserved ; 
according to the rostrum, the eye-stalks, and the ext. br. of urp., 
it belongs to “ Serg. brachyorrhos Kr.,” which is the youngest 
Mastigopus of S. edwardsii Ky. (P. Z.8. 1896, pp. 963-64). 
SERG. PREHENSILIS Bate, p. 385, pl. xxi. (Plate XI. figs. 4a, 
4b.) 
Bate has examined one specimen from Stat. 236, lat. 34° 58’ N., 
Jong. 139° 29' E., off Japan, 775 fathoms. The type, an adult 
male, has been preserved; it differs from all other species known 
tome. It will be useful to redescribe its most essential characters, 
and two new figures are given (Pl. XI. figs. 4a, 46). The 
