34 DISCOVERY REPORTS 



slit is somewhat wider and I can find no trace of a proximal dilatation. None of the Discovery females 

 is fully mature and, although this difference may be due to immaturity, I am inclined to think there is 

 a slight sexual dimorphism in this structure. 



Specimens of all sizes from 34 mm. to 173 mm. are present in the Discovery material and from the 

 tabulated measurements given in Table 1, it can be seen how the various growth changes progress. 



The pleopods are alike in both sexes and no brush of setae is developed on the antennules of the 

 males. Brood lamellae do not begin to develop until the females are about 60 mm. in length and it is 

 difficult to see the male tubercle at the base of the eighth thoracic appendage until the males are even 

 longer. Fage (1936, p. 146) recorded that in specimens of Gnathophansia each thoracic sternum bore 

 a rounded boss, which differed in shape and armature in the two sexes. The Discovery specimens have 

 been in preservative for a long time and any attempt to bend back the thoracic appendages to expose 

 the sterna would cause damage to the animals. I have therefore not attempted to ascertain the sex 

 of those specimens in which brood lamellae or the male tubercle are not easily visible. 



Size. The largest specimen of G. ingens ever recorded was a male which measured no less than 

 210 mm. from the tip of the rostrum to the apex of the telson. The largest recorded female was adult 

 with a very large empty brood sac and measured 157 mm. The largest male in the Discovery collection 

 has the tip of the rostrum broken, but I estimate that its full length was about 176-7 mm. A slightly 

 smaller undamaged male measures 173 mm. The largest female measures 156 mm., but is still quite 

 immature with small narrow oostegites. 



Colour. There is some evidence that the colour becomes more red and less orange-brown as the 

 animals mature. At station 1761 a young specimen of 37 mm. is described as 'Deep orange-brown' 

 and at station 177 another young specimen of 38 mm. is said to be 'Orange-brown'. A large male of 

 about 130 mm. from station 86 is labelled 'Deep scarlet red throughout, palest on scales, uropods and 

 protopodites of pleopods' and at station 1770 an immature specimen of 70 mm. is said to be 'Deep 

 brilliant scarlet throughout '. 



Distribution. G. ingens has been recorded from widely separated localities in the tropical and sub- 

 tropical waters of the world. The type was taken off the west coast of Africa and the Challenger 

 specimen from between North Australia and New Guinea. Since then it has been recorded on a 

 number of occasions off the coast of California, near the Hawaiian Islands, the Philippines and New 

 Guinea in the Pacific (W. M. Tattersall, 1951); the Central Arabian Sea, off Zanzibar and near the 

 Seychelles in the Indian Ocean (W. M. Tattersall, 1939); from the Gulf of Mexico and south of the 

 Azores in the western North Atlantic and from off the coast of South Africa in the eastern South 

 Atlantic. 



The Discovery records, most of them from around the coast of South Africa, extend its known 

 range in the south-west Indian Ocean. The capture of a specimen from east of La Plata is the first 

 record from the western side of the South Atlantic. Its occurrence in latitudes 41 ° 37' N. and 

 37 50' S. proves that it extends into the temperate waters of both northern and southern hemispheres. 



Where closing nets have been used and it is possible to tell the exact depth of capture, it has been 

 found to be most common between 600 m. and 1500 m. At station 101 it was taken between 2480- 

 2580 m. (Hansen, 1927, records it from 2470-3990 m.) while at station 1770 it was taken in a closing 

 net fishing between 340-210 m. It is thus evident that it has a very considerable vertical range. 



