224 PROFESSOR CHARLES CHILTON ON THE 



acute, those of both the first and second perseopoda being acutely produced in front ; 

 the eye is large, showing a little colour in the spirit specimens and probably having 

 been red in the living animal, but it is not so large as in the Saldanha Bay specimen. 

 The terminal joints of the peneopoda are rather wide distally, as shown in STEBBING'S 

 figure. 



It seemed possible, therefore, that after all we might perhaps be dealing with two 

 species : one P. antarctica, with side plates more or less acutely produced in front, the 

 other P. tenuipes (including P. osborni and P. atolli), in which some of the side plates 

 were rounded in front, although, as already shown, the differences did not appear to be 

 constant. Considerable interest was therefore attached to the examination of the 

 specimens from Ceylon referred by WALKER to Tritseta antarctica, to see if they were 

 really distinct from P. atolli. It was found that in some points they are a little 

 nearer to P. antarctica than the type specimen of P. atolli is ; thus, for example, the 

 side plates of the first gnathopod are acutely produced in front as in P. antarctica ; the 

 side plates of the second gnathopod, however, are rounded below. The side plates of 

 the first and second perseopoda cannot be very clearly made out, but they appear to 

 be fairly acute in front, though projecting rather more posteriorly than shown in 

 STEBBING'S figure. In other points, however, these Ceylon specimens were clearly the 

 same as P. atolli, and the eye is large and shows little colour in the spirit specimens. 

 Consequently, after considerable hesitation, I was forced to remain at the conclusion at 

 which I had previously arrived, that it is impossible to separate the various forms into 

 two species. The species has more recently been recorded from the east coast of Africa 

 by Mr WALKER under the name of P. atolli, and it was some confirmation of the 

 conclusion I arrived at to find that specimens in the Museum from this locality, 

 though recorded under the name P. atolli, were in the separate tube labelled by him 

 P. antarctica. 



It seems clear that here, as in other cases, we have one widely distributed species, 

 most abundant in Antarctic and sub-Antarctic seas, but extending far to the north 

 both in the Indian seas and in the Pacific, and that, although it is impossible to 

 find constant characters for the separation of it into two distinct species, there are 

 slight local differences, some showing one combination of characters, others another 

 combination. 



A small specimen of this species was among some undetermined Amphipoda, 

 collected at South Georgia in 1882-83, that were submitted to me by the authorities of 

 the Hamburg Museum. 



[After the whole discussion of this species as given above had been written, I found 

 further specimens from South Orkneys in a bottle of "residues" received in May 1912 

 from various collections made at Scotia Bay in 1903. Some of these specimens were 

 larger than those from the South Orkneys mentioned above, the largest being about 

 5 mm. long. In the largest specimens the eye was very large, and red in colour, as in 

 the Saldanha Bay and other specimens already referred to ; in smaller specimens the 



(ROY. soc. EDIN. TRANS., VOL. XLVIII., 506.) 



