54 PERCY SLADEN TRUST EXPEDITION 
Tribe PENEIDEA. 
Family Sergestidee. 
SerceEstes, Milne Edwards. 
1. Sergestes challengeri, Hansen (Plate 7, fig. 1). 
Sergestes challengeri, Hansen, Proc. Zool. Soc. London, 1903, pp- 61 and 72, pl. xi, figs. 2, a—n; Kemp, 
Proc. Zool. Soc. London, 1910, p. 641, pl. liii, figs. 2—4, pl. liv, figs. 2—5. 
Sept. 27, 1905. 8. by E. of Farquhar; 10° 27’S., 51° 17’ E.  p. 800 to 0 fms. ; one 
male, 23 mm. q. 1000 to 0 fms. ; one young, 18 mm. and fragments of a larger female. 
Oct. 16, 1905. 6 miles N.N.W. of Desroches Atoll. nn. 200 to 0 fms. one female, 
29 mm. 
This species is of particular interest in that it possesses a great number of luminous 
organs. Hitherto it was known only from a single mutilated example obtained by the 
“Challenger” expedition and described in detail by Hansen. The additional examples 
have enabled me to supplement Hansen’s account of the structure of the photophores and 
the results of this investigation have formed the subject of a separate paper”. 
The specimens are unfortunately not in good condition, but their agreement with 
Hansen’s account is so close as to leave no doubt of their specific identity with the 
‘“‘Challenger” example found in the neighbourhood of the Fiji Islands. The only points 
in which they differ from his description are that the rostrum (fig. 1) is directed forwards 
and upwards, rather more horizontally than in Hansen’s figure and with a much more 
acute apex; the hepatic spine of the carapace seems better defined and the penultimate 
segment of the second maxillipede is distinctly longer than the antepenultimate. , In the 
last feature they resemble the closely allied species S. gloriosus, Stebbing, a form which is 
also provided with photophores. In the broad apex of the antennal scale, in the develop- 
ment of the branchie and in all other details noted by Hansen there is complete 
agreement. 
The eyes, which were missing in the type specimen, extend a trifle beyond the middle 
of the basal segment of the antennular peduncle and are a little shorter than the antennal 
peduncle. In dorsal view the cornea occupies very nearly half the length of the whole 
organ; it is scarcely at all depressed and, seen laterally, its greatest length is about 
equal to its height. 
I have been able, though not without considerable difficulty, to observe the photo- 
phores in all the positions noted by Hansen and, in addition, have also found the 
following, including those of the eyes and last two pairs of pereeopods which were missing 
in the type: . 
Eye: on the under surface of the stalk, one close to the cornea and one at the 
proximal end. 
Fourth perzeopod ; two on the ischium, one at the proximal and one at the distal end, 
and one situated distally on both merus and carpus, the latter very minute. 
Fifth perzeopod: same disposition as in the preceding, but the proximal photophore 
on the ischium is missing. 
* Kemp, Proc. Zool. Soc. London, 1910, p. 639. 
