SYSTEMATIC REPORT 39 



has been recorded from the Hawaiian Islands and in the east from the west coast of the United States, 

 the gulf of Panama and the Galapagos Islands. In the South Pacific it has only been recorded from 

 Fiji and from the north of New Zealand. 



G. zoea is a bathypelagic and mesoplanktonic form and from the records it appears that young 

 specimens tend to inhabit higher levels than the adults. 



Gnathophausia gracilis W.-Suhm, 1875 



1875 Gnathophausia gracilis W.-Suhm, p. 33, figs. 



1885 a Gnathophausia gracilis, G. O. Sars, p. 48, figs. 



1891a Gnathophausia gracilis var. brevispinis Wood-Mason and Alcock, p. 187. 



1 89 1 b Gnathophausia brevispinis Wood-Mason and Alcock, p. 269. 



1893 Gnathophausia dentata Faxon, p. 217. 



1895 Gnathophausia brevispinis Faxon, p. 216. 



1900 Gnathophausia sp. Chun, pp. 289, 516, 531; 1903, p. 551, pi. 



19066 Gnathophausia bidentata Illig, p. 229, figs. 



1906 Gnathophausia gracilis, Ortmann, p. 39. 



1912 Gnathophausia gracilis, Hansen, p. 185, fig. 



1930 Gnathophausia gracilis, Illig, p. 409, figs. 



1941 Gnathophausia gracilis, Fage, p. 27, figs. 



195 1 Gnathophausia gracilis, W. M. Tattersall, p. 28. 



Occurrence: 



St. 700. 18. v. 31 (day). North-east of Cape Verde Is., 2025-0 m., 1 juv. 24 mm. 



St. 2057. 29. iv. 37 (day). North-east of St Helena, 1450-700 m., 1 imm. <J, 47 mm. (rostrum 11 mm.). 



St. 2059. 30. iv. 37 (day). North-north-east of St Helena, 1400-0 m., 1 <J, 58 mm. (rostrum 13 mm.). 



Remarks. There is probably no species of Gnathophausia in which the differences between very 

 young specimens and more mature ones are so extensive as they are in G. gracilis. This species was 

 first recorded by Willemoes-Suhm from the 'Challenger' and was fully described and figured by 

 G. O. Sars (1885 a, p. 48). The material at his disposal was not in very good condition and did not show 

 the dentate crest on the dorsal surface of the carapace in the gastric region, which is so marked a 

 character as the animals increase in size. In the specimen from station 700 this crest is very small 

 with very tiny teeth, but in the largest specimen from station 2059 it stands up as a large, somewhat 

 triangular plate with one very well-developed apical spine and clearly marked denticles. The first and 

 second abdominal somites are each armed with two strong spines on the dorsal surface in the median 

 line. The anterior spine on the first abdominal somite is very small, but the posterior one is very large, 

 as are both the spines on the second abdominal somite. In lateral view, the great development of these 

 spines gives the animals a most grotesque appearance. Fage (1941, p. 28) has recorded a character 

 which has been overlooked by previous workers — the presence of six very strong short curved teeth 

 on the inner margin of the sympod of the uropods. These spines are directed somewhat obliquely 

 downward and are difficult to detect when the appendage is in situ. 



Fage also recorded that on each of the thoracic sterna in the males there is a stout, median, some- 

 what forwardly directed spine, the one on the first thoracic somite being very small. These spines are 

 clearly present in the two. larger specimens in the Discovery collection, but they become progressively 

 smaller posteriorly and that of the eighth somite is almost imperceptible. My smallest specimen, 

 measuring only 18 mm., from the base of the rostrum to the apex of the telson, shows no trace of these 

 spines and, since Fage recorded that they were clearly developed in his smallest male which measured 

 23 mm., it is probable that mine is a young female. 



