Chilton. — Notes on some New Zealand Crustacea. 133 



doubt that they do differ considerably in habit, and perhaps should be 

 looked upon as a special variety. All the specimens found were quite 

 small, not more than 2 mm. in length, and it is, of course, possible that 

 only the young stage is passed through in the stream, and that as the 

 animals become older thev take to the sea. 



Jaeropsis curvicornis (Nicolet). 



Jaera curvicornis Nicolet in Gay's Hist. fis. y pol. de Chile, vol. 3. 

 p. 263, pi. 3, fig. 10, 1849. Jaeropsis neo-zelanica Chilton, 

 Trans. N.Z. Inst., vol. 24, p. 267, 1892. J. curvicornis H. 

 Richardson. Trans. Connect. Acad. Sci., vol. 11. p. 298, 1902 ; 

 Stebbing, Ceylon Pearl Fisheries Report, pt. 4, p. 51, pi. 11 (c). 

 1905. J. patagoniensis H. Richardson. Proc. U.S. Nat. Mus., 

 vol. 36, p. 421 (with figure), 1909. 



I have specimens of this species from Akaroa, Taylor's Mistake, and 

 Lyall Bay. The colour seems somewhat variable, the dorsal surface being 

 a light brown and legs whitish ; in one specimen, however, the brown 

 colour was present only on the posterior part of the head and the first four 

 segments of the paraeon, the remainder of the dorsal surface being whitish. 

 The Akaroa specimen, which I described in 1892 under the name Jaeropsis 

 neo-zelanica, is a very small one, only about 2 mm. in length ; one of 

 the specimens from Taylor's Mistake is considerably larger, being 5 mm. 

 in length, and comparison of this, which I have no doubt belongs to the 

 same species as the Akaroa and other specimens, enables me to give some 

 points in which the larger and presumably adult specimen differs from 

 the small immature ones. In the larger specimen the flagellum of the 

 antennae is considerably longer than in the other specimens, and consists 

 of about twelve joints, the first one being much the largest, as long as the 

 remainder together, and being broadly expanded. In this specimen, too. 

 the sides of the pleon are smooth, except for a small tooth about a third 

 the length from the posterior end. In small specimens the sides of the 

 pleon are somewhat serrated, the last serration, which corresponds with 

 the one still present in the older specimen, being slightly the most pro- 

 minent. 



All the species of this genus appear very closely similar, and from what 

 has been said above it seems probable that some of them have been esta- 

 blished on small and possibly immature specimens. I think Mr. Stebbing 

 is right in uniting J. neo-zelanica with J. curvicornis (Nicolet), and the 

 specimens which he describes from the Gulf of Manaar certainly seem to 

 be close enough to be placed under this species. I have no doubt also 

 that the specimens more recently described by Miss H. Richardson under 

 the name J. patagoniensis also belong here, the pleon agreeing closely with 

 that of my larger specimen ; the other points she mentions, as regards 

 colour, &c, are hardly of specific importance ; the lobe at the front of the 

 head is described and figured by her as having a small point in the centre, 

 while in my specimens it is rounded in front. Nicolet draws his specimens 

 with this lobe slightly concave in front, and, in any case, the difference 

 appears to be very trifling. J. marionis Miers, taken by the " Challenger " 

 off Marion Island, seems to be pretty closely allied, but, as represented 

 by Miers, has the joints of the antennae much less expanded, and the 

 uropoda are perhaps rather different in structure. 



