DESCRIPTION OF SPECIES 3ai 



the third measures 7 mm., the fourth 11 mm., and the fifth 14 mm. in length. There 

 is a deep longitudinal groove on the dorsal surface of each of the last three peduncular 

 joints. The flagellum is considerably shorter than that of the antennule ; it measures 

 1 1 mm. in length and consists of only seventeen joints. 



The basipodite of the maxilliped is separated from the lamella by a suture ; the suture 

 between the coxopodite and the epipodite is not so easy to trace, but it appears to 

 be present. As in the other deep-sea forms a small tubercle, covered with hairs, is 

 present near the base of the second joint of the palp. 



The propodus of the second thoracic appendage is broad, and its inner margin is 

 armed with a row of thirty-four somewhat triangular processes alternating with a row 

 of modified spines, the detailed structure of which it was not possible to make out. The 

 inner distal extremity of the carpus is crenulate and bears two short spines. The re- 

 maining thoracic appendages are slender ; as in S. bromleyana, Suhm, the fourth joint 

 is longer than either the third or the fifth. The setae, which are restricted to the distal 

 ends of the propodus, carpus and merus, and to two groups on the outer margins of the 

 merus and the carpus, are all of the simple variety. 



The sterna of the abdominal segments are produced backwards in the median line 

 and the resuhing spines increase in size from before backwards. The protopodite of 

 each of the first three pairs of pleopods is large, and roughly triangular in shape ; I have 

 been unable to see any spines on the produced angles. The suture of the exopod of both 

 the fourth and fifth pleopods is oblique, and in both cases the endopod is entire. 



Distribution. Off Coats Land, in 2759 m. 



A considerable amount of confusion surrounds the identification of the two following 

 species, S. trilobitoides, Eights (PI. XIV, fig. 7) and S. cornuta, Studer (PI. XIV, fig. 6). 

 The former species was described by Eights in 1833 and the latter by Studer in 1879, 

 although he mentioned it in an earlier paper ( 1 876) under the name of Brongniarta cornuta. 

 Neither the descriptions nor the figures are detailed or accurate, and since the two species 

 are very much alike and have never both been recorded, until now, in any single collection, 

 and since Studer (1879) does not bring out the main points of difference between the 

 two, it is easy to see how such confusion has arisen. 



Beddard (18846), in his account of the Challenger Serolids, describes and figures 

 certain specimens (pp. 49-53) which he assigns to S. cormita. I have examined these 

 specimens at the British Museum and compared them with those of the present collec- 

 tion and I have come to the conclusion that his specimens are S. trilobitoides and not 

 S. cornuta, and that actually S. cornuta is not represented in the Museum collection. 



Hodgson (1910), who redescribed S. trilobitoides, considers that the two species are 

 identical, for he says, "I have, I think, satisfactorily proved that S. cormitus, Studer, is 

 merely the immature form of S. trilobitoides, Eights", and he includes S. cornuta as a 

 synonym of S. trilobitoides. In so far as Hodgson's results are drawn from existing 

 literature and since Beddard 's figures prove to be those of S. trilobitoides and not 



