13 



female is not far from being 62 mm. long, thus about as large as the largest specimen measured 

 by Alcock; the male is not inconsiderably shorter than the female. 



Remarks. — S. bisulcatus is allied to the common North-Atlantic form S. robustus 

 Smith, but differs in having the cervical furrow very pronounced on the dorsal surface of the 

 carapace, another shape of the rostrum, proximal half of third joint of the antennulêe less thick, 

 and in some other particulars; the petasma is very different from that in S. roóustus. As pointed 

 out above, S. bisulcatus Faxon (= S. bisulcatus Stebbing) is another species, which must keep 

 its older name S. phorcus Faxon. 



Distribution. — According to Alcock this species is common in the Bay of Bengal, 

 the Arabian Sea, and the Andaman Sea; the depths recorded are from 145 to 902 fathoms. 



5. Sergestcs Challengeri H. J. H. PI. I, figs. \a — <\k. 



1903. Sergestes Challengeri H. J. Hansen, Proc. Zool. Soc. London for 1903, vol. I, p. 61, 



PI. XII, figs. 2a — 211. 

 191 3. Sergestes challengeri Stanley Kemp, Trans. Linn. Soc. London, Zool. 2. ser., Vol. XVI, 



pt I, p. 54, PI. 7, fig. 1. 



Stat. 46a. April 7. Lat. 8° o'. 5 S., long. 11834'./ E. 1600 m. Deep sea tjawl. 1 adult female. 

 Stat. 89. June 21. Pulu Kaniungan ketjil. 11 m. Shore exploration. 1 immature male. 

 Stat. 141. Aug. 5. Lat. i°o'.4S., long. i27°25'.3E. 1950 m. Hensen vertical net, from 1500 m. 



depth to surface. 2 females. 

 Stat. 143. Aug. 7. Lat. i°4'.5 S., long. 127° 52'.6 E. 1454 m. Hensen vertical net, from 1000 m. 



depth to surface. 2 young specimens. 

 Stat. 148. Aug. 10. Lat. O if.6 S., long. 129 14.5 E. 1855 m. HENSEN vertical net, from 



IOOO m. depth to surface. 1 adult male, 2 immature specimens, and 1 Mastigopus. 

 Stat. 185. Sept. 12. Lat. 3°2o'S., long. i27°22'.9E. Hensen vertical net, from 1536 m. to 



surface. 5 adult males, 4 females, 2 immature specimens. 

 Stat. 243. Dec. 2. Lat. 4°30.2S., long. i29°25'E. Hensen vertical net, from 1000 m. to 



surface. 2 young specimens. 



a. Adult Specimens. — This species was established on a single mutilated specimen. 

 A large number of luminous organs were pointed out, and no other species with such organs 

 was known. In 1905 Stebbing described an allied species, 5". gloriosus, from off South Africa, 

 but in this form the luminous organs are still considerably more numerous than in S. Challengeri, 

 and the animal is much larger. In the manuscript to the paper on the Sergestidae from the 

 "Travailleur" and "Talisman" I have described a third species secured by the last-named 

 expedition in the tropical Atlantic; this species, which I name S. splendens n. sp., is as large 

 as S. gloriosus, viz. about 50 mm. in length, but it differs from S. gloriosus and agrees nearly 

 with 5". Challengeri as to the number of luminous organs. Finally, the "Siboga" has captured 

 many specimens of a fourth species, to be described later on, S. fulgens n. sp. ; it is about as 

 large as S. gloriosus and S. splendens, while the largest specimen of S. Challengeri hitherto 

 seen is only 35 mm. long, and most of its specimens are less than 30 mm. These four luminous 

 species are very closely allied, in reality very similar in most features; S. gloriosus must be the 

 most easy to determine as it has a much higher number of luminous organs on the antennal 

 squama, the sides of the carapace etc. than found in the three other species. 



