AMPHIPODA OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 511 
two-thirds as long as the propod. The third uropods have the branches equal in length 
and rather longer than the peduncle. In other respects the specimen agrees fairly well 
with SressBine’s description, and the lateral lobe of the head is acutely pointed as in 
that species. 
The form that I consider the immature male differs from the female in the second 
gnathopods (fig. 33), which are of the same general shape, with a moderately long carpus 
but with the propod larger and stouter, its palm more oblique and bearing three short 
conical acute teeth, one near the base of the finger, one beyond the point on which the 
end of the finger impinges, and one midway between these two. The third and fifth 
perzeopoda are peculiar in having the merus widely dilated so as to be fully half as 
broad as long (see fig. 34); in the fourth pereopod the merus is of the usual shape. 
Whether this expansion of the merus is a sexual character, or an individual variation 
in the particular specimen examined, I cannot say. 
Genus JASSA. 
Jassa falcata (Montagu). 
Cancer (Gammarus) falcatus Montagu, 1808, Trans. Linn. Soc., vol. ix. p. 100, pl. v. fig. 2. 
Podocerus falcatus and P. validus Stebbing, 1888, p. 1132, pl. cxix., and p. 1135, pl. cxxxviii.B. 
»  tmgens Pfeffer, 1888, p. 131. 
is australis Haswell, 1880, p. 338, pl. xxi. fig. 8. 
Jassa pulchella Stebbing, 1906, p. 654. 
» yy Chilton, 19094, p. 647. 
» goniamera Walker, 1903a, p. 61, pl. xi. figs. 98-106a. 
»  wandelt Chevreux, 19068, p. 94, figs. 54-56. 
» falcata E. W. Sexton, 1911, p. 212. 
[I have given only the chief references relating to the occurrence of this species in 
southern seas. The very numerous references to its occurrence in the northern 
hemisphere can be readily traced from those here given. | 
South Orkneys, Scotia Bay, Station 325, and Macdougal Bay, Station 326s. 
Several specimens of both sexes and of various ages. 
Station 414, lat. 71° 50’ S., long. 23° 30’ W.; vertical net, from surface to 
1000 fathoms. 15th March 1904. One specimen. 
Mrs Sexton, who has specially studied this species, believes that there are at least 
two different forms of the adult male. 
When I came to examine the South Orkneys specimens it became quite clear that 
some of them were almost, if not quite, the same as the northern species, and that the 
males belonged to what Mrs Sexton has described as the “second form.” ‘The males 
agree almost exactly in the characters given of the second antenna and of the 
enathopods for this form; and females of this form were also present. As there are 
two forms known of this species in European seas, it was to be expected that, if the 
South Orkneys species was really the same species, the “first form” would also be 
found there. This actually proved to be the case, for two specimens from Macdougal 
TRANS. ROY, SOC. EDIN., VOL, XLVIII. PART IT. (NO, 23). 76 
