44 DISCOVERY REPORTS 



Stage I. The carapace retains in this, and even in later stages up to about 9 mm., a trace 

 of the anterior marginal spine. Somites i and 2 have no dorsal spine, while those of 

 somites 3-6 are very small, or even lost. 



In the material submitted to Mr Burkenroad he has found one differing from the 

 others in having neither hepatic nor supraorbital spine. In the material remaining, from 

 1935 and 1938-9, we have found none which lack this spine (37 specimens of 7 mm. and 

 more). Measurements of the single specimen without hepatic spine as compared with 

 others of about the same size show no significant differences except that the eye is 

 shorter and the eyeball smaller. It is impossible, among the remaining specimens to 

 detect any specific differences, though such differences might perhaps appear if a 

 sufficiently large material could be measured. 



Sergestes corniculum Form B 



Acanthosoma 2 (Fig. 36 a-c). Length 2-62 mm. Rostrum 0-78 mm. 



Rostrum longer than antennule. Carapace a little broader than long. Supraorbital 

 spine longer than eye ; hepatic spine slender, not swollen at base ; anterior lateral spine 

 with two long spinules only. Posterior dorsal spine absent. Dorsal organ a slender 

 papilla. Dorsal spines of abdomen small on somites i and 2, longer on 3-6, that of 

 somite 4 the longest. Lateral spines shorter than in species A and with few long spinules, 

 that of somite 5 with one long spinule only. 



Eye very large, with anterior papilla, its length about one-fifth length of body and 

 not much greater than width of eyeball (1-23 : i). Antennal scale very slender; flagellum 

 1-7 mm. Exopod of uropod with setose part nearly twice the bare part (i-8 : i) and 

 length eight times the width. Somite 6 with dorsal setae. Arms of telson fork with 

 one inner, one outer, and one dorsal spine. 



The description is from a specimen taken at Bermuda on 5 July 1938, which moulted 

 from stage i . Specimens of the same form, which appears to belong to the same species 

 as was described by Hansen, have been examined from the following Discovery Stations : 



— 8° 30' N, 17^53' W, 701. 14° 39' N, 25° 51' W, 



— 34° 33' N, 14° 32' W, 703. 7° 17' N, 28° 02' W, 

 281. oo°46'S, S°49'E, 704- 3' 37' N, 29° 14' W. 



At Station 281 Elaphocaris of type A were also taken. If these really belong to the 

 Acanthosoma with which they were associated the Elaphocaris B described must 

 represent a third species as yet unknown; but it is possible that the Elaphocaris of 

 Station 281 belongs to the Acanthosoma described below as form C, from the adjacent 

 Station 282. 



Sergestes corniculum Form C 

 Material. 



Discovery Stations: 278, off Port Gentil, French Congo; 282, 1° 11' S, 5° 38' E; 706, 3° 26' S, 



32° 08' W. 



Description. Acanthosoma 2 (Fig. 36 d). Length 3-39 mm. Rostrum 1-39 mm. 



