PARACOROPHIUM EXCAVATUM.— CHILTON. 45 



from Lake Roto-iti (fresh water) in Auckland which I afterwards identified as. 

 belonging to the same species.^ The Brisbane specimens now to be described 

 also come from brackish water, and the occurrence of this species, which is 

 apparently confined to brackish and fresh waters, in Australia as well as in 

 New Zealand, is of some importance in connection with the general question of 

 the geographical distribution of New Zealand and Australian Amphipoda.^ 



In 1899 Stebbing established the genus Paracoropliium for the reception 

 of the species now under consideration, which is the only one of the genus at 

 present known. 



PARACOROPHIUM Stebbing, 1899. 

 Panworophium Stebbing, 1899, Ann. Nat. Hist., ser. 7, vol. 3, p. 350; 1906, Das Tierreicli 

 Aniphipoda, p. 663. 



In general appearance and in most of the appendages Paracorophium 

 comes close to Corophium, the chief points of difference being — (1) The 

 mandible has the palp well developed and three-jointed, (2) the second 

 gnathopod of the male is markedly different from that of the female and in. 

 both sexes has the merus produced into a scoop-like process different from that 

 in Corophium, (3) the third uropoda are two-branched. 



PARACOROPfflUM EXCAVATUM (G. M. Thomson). 

 Corophium excavatum G. M. Thomson, 1884, Trans. N. Z. Inst., voh 16, p. 236, pi. 12, fig. 1 to 8: 

 Paracorophium excavatum,, Stebbing, 1906, Das Tierreieh Amphipoda, p. 664. 

 Paracorophium excavatum, Chilton, 1906, P.Z.S., p. 704. 



As this is the only species of the genus it is unnecessary to give a separate 

 specific diagnosis. Thomson's original description and figures, on which that 

 in Das Tierreieh Amphipoda appears to be based, apply to an immature male. 

 A detailed description is given below. 



>S''i^e.— About 4 mm. in length. 

 Colo ur. — Greyish. 



Localities. — New Zealand — Brighton, Napier, Nelson (brackish water), 

 and Lake Roto-iti (fresh water) ; Australia — Brisbane River (brackish). 



Anienna 1 (fig. 1) has the second joint of the peduncle longer than th<^ 

 first but much more slender ; the third about half the length of the second ; 



- P.Z.S. 1906, p. 704. 



' Several of the Corophiidse appear to be able to live in brackish or fresh water. Speaking 

 of the whole family Stebbing says (1906, p. 662), "Marine, bnt extending into brackish or even 

 almost fresh water ' ' ; and of Corophium crassicorne Bruz. he says, ' ' Found in Norfolk in 

 almost fresh water. ' ' C. volutator is recorded as * ' forming tubular galleries in the mud of 

 tidal swamps. " " I have specimens of this sjiecies obtained for me by Mrs. Sexton, of Plymouth, 

 labelled ' ' Mouth of Issel, near Kampen. Quite fresh water ' ' ; and Mr. Eobert Gurney, 

 speaking of this species under the name "C grossipes (Linn.)," says "it seems to thrive- 

 well in fresh water'' (Trans. Norfolk and Norwich Naturalists' Soc, vol. viii, p. 435, 1907). 

 Later on he recorded it as found in the Oued Tindja at its outflow from Lake Garaa AchkeJ^ 

 in Tunisia (Jour. Roy. Micr. Soc. 1909, p. 283). 



