36 DISCOVERY REPORTS 



Gnathophausia gigas W.-Suhm 1873 



1873 Gnathophausia gigas (lapsus calami) W.-Suhm, p. 400, figs.. 



1875 Gnathophausia gigas W.-Suhm, p. 28, figs. 



1885 a Gnathophausia gigas, G. O. Sars, p. 33, figs. 



1905 Gnathophausia drepanephora Holt and Tattersall, p. 113, figs. 



1906 Gnathophausia gigas, Ortmann, p. 36, figs. 

 1941 Gnathophausia gigas, Fage, p. 24, fig. 

 1943 Gnathophausia gigas, Nouvel, p. 12, figs. 



195 1 Gnathophausia gigas, Tattersall and Tattersall, p. 77, figs. 



Occurrence : 



St. 9. 11. ii. 26 (day). Midway between Gough I. and South Georgia, i25o(-o) m., 1 <$, no mm., 1 juv. 48 mm. 



St. 71. 30. v. 26 (day). North-east of Falkland Is., 200o(-o) m., 2 juv. 47 mm. 



St. 72. 1 vi. 26 (night). North-east of Falkland Is., 200o(-o) m., 1 juv. 57 mm. (blood red), 1 juv. 46 mm. (more 



orange tone). 

 St. 76. 5. vi. 26 (day). Midway between Gough I. and Bahia, Argentine, i50o(-o) m., 1 juv. 65 mm. 

 St. 86. 24. vi. 26 (day). West of Cape Town, iooo(-o) m. 5 small specimens too damaged to measure. 

 St. 100. 4. x. 26 (day). West of Cape Town, 2500-2000 m., 1 juv. 40 mm. 

 St. 101. 15. x. 26 (day). West of Cape Town, 1310-1410, 3 juv. 60-34 mm. 

 St. 114. 12. xi. 26 (day). North-east of Bouvet I., 700-650 m., 1 juv. 38 mm. 

 St. 239. 2. vi. 27 (day). North-east of South Georgia, i350-io5o(-o) m., 3 juv. 37-38 mm. 

 St. 253. 21. vi. 27 (day). West of Cape Town, 1050-1000 m., 2 juv. 37 and 45 mm. 



St. 391. 18. iv. 30 (day). Midway between South Georgia and Cape Horn, 1300-1200(^0) m., carapace only. 

 St. 413. 21. viii. 30 (day). West of Saldanha Bay, South Africa, 2200-i6oo(-o) m., 2 juv. 34-37 mm. 

 St. 1298. 2. iii. 34 (day). Ice Edge, Bellingshausen Sea, iooo(-o) m., 4 juv. 1 10-37 mm - 

 St. 1755. 29. iv. 36 (day). Indian Ocean, south-south-east of Mauritius, 1700-0 m., 1 juv. 46 mm. 

 St. 1775. 27. v. 36 (night). South-east of Tristan da Cunha, 1500-1000 m., 1 damaged juv. ca. 35 mm. 

 St. 1798. 12. 6. 36 (night). North-east of Bouvet I., 1000-750 m., 1 juv. (typical drepa?iephora stage) 39 mm. 

 St. 1991. 11. iii. 37 (day). South-east of South Georgia, 1500-1000 m., 1 damaged juv. ca. 35 mm. 

 St. 2022. 28. iii. 37 (night). North-west of Bouvet I., 700-400 m., 1 juv. 35 mm. 



Remarks. Growth changes similar to those which occur in Gnathophausia ingens take place in 

 G. gigas also. The relative length of the rostrum and of the spines arming the carapace tends to decrease, 

 the number of teeth on the outer margin of the antennal scale increases from one or two to five or six 

 and the epimera of the sixth abdominal somite, which are separate in young animals, gradually become 

 confluent and then fuse on the ventral surface of the somite to form a single epimeral plate. This 

 plate is of the same shape as that of G. ingens, but its lappets are not bifid and are well separated with 

 a tendency to curve outward at their distal ends. 



The postero-lateral spine of the carapace is at no time as long as it is in G. ingens. Even in very 

 small animals it does not extend beyond the posterior margin of the first abdominal somite and in 

 really large specimens it is practically obsolete. None of the Discovery specimens is mature and I can 

 see no trace of incubatory lamellae in any of them, although many of them are larger than specimens 

 which have been recorded as definite females by other workers. In Table 2, I give measurements of 

 the Discovery specimens. 



Distribution. Gnathophausia gigas is one of the most widely distributed of all mysids. The type 

 was collected by 'Challenger' at 2200 fm. to the west of the Azores. Since then it has been recorded 

 from many localities in the Atlantic from Greenland (Stephensen, 1933), the east coast of North 

 America (Ortmann, 1906; W. M. Tattersall, 195 1), the Azores, mid-Atlantic and Bermudas (Fage, 

 1941 ; Nouvel, 1943), west of Ireland (Holt and Tattersall, 1905), Madeira and Cape Verde Islands 



