KEMP—PELAGIC CRUSTACEA DECAPODA 595 
Fourth and fifth abdominal somites: one additional photophore on each in the mid- 
ventral line. 
Sixth abdominal somite: an additional organ on each side of the infero-lateral margin 
in the anterior quarter. 
These twenty-two additional organs bring the total number known in the species up 
to 139, and more will doubtless be found on the third maxillipedes and on the second 
and third legs which have been wanting in all examples which have been examined. 
A schematic view of the ventral surface of the cephalothorax and abdomen, showing the 
disposition of the photophores, will be found in the accompanying text-figure™. 
Mr Gardiner informs me that on each occasion when this species was taken he noted 
the presence of phosphorescent prawns in the townet. This observation is 
of importance, being, so far as I am aware, the only occasion on which light 
has been seen to issue from a compound luminous organ or photophore in 
a Decapod crustacean. 
The closely allied Sergestes gloriosus, described by Stebbing from the 
S. African coast, may be distinguished from the present species by the much 
narrower apex of the antennal scale. It also possesses a far greater number 
of photophores ; but, seeing that the example described measures 50 mm., 
whereas the largest known individual of S. challengeri is only 29 mm. in 
length, this character may not prove reliable, for it is by no means im- 
probable that the number of these organs increases with age. In this 
connection it may be mentioned that in the male specimen of S. challengers, 
23 mm. in length, the petasma is rudimentary. 
In Stebbing’s figure of the ventral surface of the eye only one photo- 
phore is shown, the proximal one, which is very distinct in the present 
Species, being omitted. 

2. Sergestes gardinert, sp. nov. (Plate 7, figs. 2—5). 
SSonom (9004 Ss) by why von Harquhar; N07 272) a Zak: 
p. 800 to 0 fms.; two young, badly damaged. gq. 1000 to 0 fms.; three 
males, three females, 15—24 mm. sg, 750 to 500 fms. ; one female, 20 mm. 
Oct. 6, 1905. Between Providence and Alphonse Ids.; 8° 16’ S., 
51° 26’ KE. aa. 900 to 0 fms. ; one male, 17 mm. 
Oct. 16, 1905. Five miles off Desroches Atoll. Il. 750 to 0 fms. ; one 
male, 21 mm. 
The rostrum is high and projects obliquely upwards and forwards 
(fig. 2). The apex is slender and acutely pointed and extends well beyond 
the front. There is a prominent tooth in the middle of the dorsal edge. 
The antero-inferior margin is concave, as is also the dorsal margin between 
the tooth and the apex. 
On the carapace there is no post-ocular spine and the hepatic is represented merely 

* The black spots represent photophores and the circles the points of origin of the thoracic and abdominal 
appendages. The divisions between the somites are shown by dotted lines. 
