ISOPODA. 51 



1899, Jaeropsis, Norman, 'Ann. Nat. Hist.,' ser. 7, vol. 4, p. 291. 



1900, Jaeropsis, H. RICHARDSON, ' Amer. Naturalist,' vol. 34, No. 400, p. 298. 

 1902, Jaeropsis, H. Richardson, 'Trans. Connect. Acad. Sci.,' vol. 11, p. 298. 



By the addition, which is well justified, of Jcera curvicornis, Nicolet, Miss 

 Richardson is able to say iu 1902 that " six species of this genus have been hereto- 

 fore described." They are J. curvicornis (Nicolet) ; ./. brevicornis, Koehler ; 

 ./. marionis, Beddard ; J. neo-zelanica, Chilton ; J. lobata, Richardson ; J. dolljusi, 

 Norman ; to which on the same occasion Miss Richardson adds J. rathburue. 

 Jcera antarctica, Pfeffer, may perhaps belong to the group, but the description and 

 figures leave its generic location quite uncertain. All the species have many features 

 in common. They range in size from 2 millims. to a little over 4 millims. The sides 

 of the middle body or perseon are nearly or quite parallel, with the segments very 

 distinctly separated. Both pairs of antennae are short. The appendages of the 

 peraeon are truly isopodous, without any real distinction between gnathopods and 

 peraeopods. The uropods are small, carrying two minute dissimilar rami, and 

 occupying emarginations in the distal border of the caudal shield. In the second 

 antennae the joint numbered second by Koehler, third by Chilton, Beddard, and 

 Richardson, fourth by Canon Nohman, is broadly expanded, unless J. marionis be 

 an exception, for in that species the joint is figured as cylindrical rather than 

 laminar. 



It may perhaps be objected that there is a want of authority for the statement that 

 the uropods occupy emarginations in the telsonic segment. Miss Richardson indeed 

 savs that her species, J. lobata, differs from Koehler's " in the shape of the 

 terminal segment, which is perfectly rounded in J. brevicornis," while in ./. lobata 

 " there are two posterior incisions for the reception of the uropods." But one may 

 easily press too far the differences shown in the habitus figures of very minute 

 animals. When the highly magnified figure of the uropod of J. brevicornis is 

 considered, it will be noticed that the outer margin is serrate, and this makes it 

 probable that here as in other species it has its share in completing the curve of the 

 tail-piece. 



Jaeropsis curvicornis (Nicolet) -Plate XI. (C). 



1819, Jaera curvicornis, Nicolet, in Gay's ' Hist. fis. y pol. de Chile,' Zool., vol. 3, p. 263, pi. 3, fig. 10. 



1891, Jaeropsis neo-zelanica, Chilton, ' Trans. New Zealand Instit.,' p. 267. 



1902, Jaeropsis curvicornis, H. Richardson, 'Trans. Connect. Acad. Sci.,' vol. 11, p. 298. 



The body, as described by Nicolet, forms a rounded longitudinal medio-dorsal 

 elevation. This is not particularly easy to see, but, when the specimen is placed 

 back downwards, its rolling from side to side is evidence of the shape in question. 

 The head corresponds with Chilton's description as being " produced slightly into a 

 rostrum between the bases of the antennae ; end of rostrum emarginate, and with a 



H 2 



