AMPHIPODA OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 221 







Polycheria antarctica Stebbing, 1906, p. 520. 



Walker, 1907, p. 34. 



Trit&ta osborni Caiman, 1898, p. 268, pi. xxxii. fig. 2, and p. 288. 

 Pohjcheria at oil i Walker, 1905, p. 926, pi. Ixxxviii. figs. 1-5. 



Entrance to Saldanha Bay, Station 483. One specimen, 6 mm. long. 

 South Orkneys, Scotia Bay, Station 325. Many specimens, all of small size, 

 averaging 2 mm. in length. 



The specimen from Saldanha Bay is, I think, specifically identical with the 

 Challenger form described under the name Tritgeta kergueleni. The eye is very large, 

 occupying the greater part of the side of the head ; the posterior angle of the third 

 pleon segment is quadrate, with a very short tooth, and the pleon and urus have the 

 carination described, though to a less degree ; the antennae agree with the description 

 as regards the proportions of the joints, the lower being a little longer than the upper ; 

 the branches of the third uropods are slightly unequal. 



In the large eye and in other essential points it also agrees with P. tenuipes Has- 

 well, and with P. obtusa G. M. Thomson, whose description of the terminal joints of 

 the perasopoda applies exactly to the specimen under consideration. In describing 

 his specimen Mr THOMSON pointed out that it was probably the same as P. tenuipes 

 Haswell. On the other hand, the Saldanha Bay specimen differs from the Kerguelen 

 Island one in the side plates, which are not so acutely produced anteriorly. 



The specimens from South Orkneys are all small. The eye is of much smaller size, 

 and the carination of the pleon is absent altogether or only slightly marked ; the joints 

 in the flagella of the antennae are fewer in number, and the two antennae are about 

 equal in length ; the outer branch of the third uropod is only about half the length of 

 the inner ; both the third and the fourth side plates are produced anteriorly into 

 an acute lobe exactly like that figured by STEBBING for P. antarctica (1906, p. 520, 

 fig. 91). In this respect, therefore, they differ from his description of P. tenuipes, with 

 which they agree in some of the other points mentioned, for that species is described 

 in Das Tierreich Amphipoda as having the fourth side plate reduced to a short, blunt 

 lobe, this character being apparently taken from CALMAN'S description of P. osborni, 

 which STEBBING gives as a synonym of P. tenuipes. 



These South Orkneys specimens are apparently immature, although the characteristic 

 form of the terminal joints of the perseopoda and of the third and fourth side plates is 

 already present, and I think there can be no doubt they belong to the same species as 

 the Saldanha Bay specimen. In the smaller eye they resemble P. brevicornis Haswell, 

 which does not seem to be separated from P. tenuipes by any other character of 

 importance. Mr WALKER (1907, p. 34) has pointed out that HASWELL'S description of 

 the second gnathopod of P. tenuipes and of P. brevicornis, and his figure of that of the 

 first species, are quite unlike those of P. antarctica. The figure is undoubtedly very 

 rough and insufficient, but the descriptions, so far as they go, are not inconsistent with 



(ROY. 8OC. EDIN. TRANS., VOL. XI.VIII., 5(13.) 



