GENUS OF TEfeREStRiAL ISOPODA. 451 



New Zealand in 1907 ; subsequently Prof. Benham sent me a male and a 

 female from the same locality, and quite recently Mr. Walter Traill has sent 

 me two males and one female from the island of Ulva in Paterson Inlet, 

 Stewart Island. 



Filhol states that he collected the species near Wellington, but, though I 

 have made many collections there, both personally and by the help of friends, 

 I have not succeeded in finding it in that locality. 



I feel confident that the species described by Nicolet from Chili are the 

 same as the New Zealand one ; his figures * and description agree throughout, 

 the large expansions of the first perseon segment in the male are quite 

 characteristic, and his figure of the antenna of Oniscus hucculentus agrees 

 closely with the one I now give (fig. 48), which was drawn before I had 

 seen the plates of Nicolet's work. The form Nicolet described as 0. tuber- 

 culatus is evidently the female, and, though he described it as a different 

 species, he recognised that it resembled 0. bucculentus except for the secondary 

 sexual characters peculiar to the male. 



A comparison of this species with D. aucJclandice gives us a good example 

 of the apparent capriciousness in the secondary sexual characters of these 

 Crustacea. In D. aucklandice the differences are confined to the antennae 

 and the tuberculation of the body ; in I), lucculentus we have similar sexual 

 differences, though to a loss degree, but in addition we have in the male the 

 extraordinary balloon-like expansions on the first perseon segment, for which 

 I know of no parallel among the Crustacea. What the function of these 

 can be it is difficult to imagine ; they appear, however, only to be developed 

 to the full extent in the adult male; I have one specimen, a male, showing 

 the usual male structure of the first and second pleopods, but the expansions, 

 though large, are not so large as shown in fig. 45, taken from an older male, 

 and their outline is slightly angular, indicating the normal shape of the 

 segment; Filhol's figure shows a male in about the same stage of develop- 

 ment ; his figure, however, is poor, and shows the legs much too long — 

 when in their normal position they are not visible in dorsal view. 



Fig. 45 of the male is taken from a Chatham Islands specimen ; in it the 

 balloon-like expansions are somewhat flattened below, but very convex above, 

 and the surface is thickly covered with minute spinules just as is shown in 

 Nicolet's figure. In a specimen subsequently received from Paterson's 

 Inlet, Stewart Island, the expansions are still larger and somewhat more 

 separated from the segment itself ; they are almost globular and strongly 

 convex below as well as above, and the surface is almost smooth, showing 

 only a slight wrinkled appearance, but apparently no minute spinules. The 

 expansions are surrounded by a fairly thick chitinous integument, quite firm 



* I am indebted to Dr. W. T. Caiman, of the British Museum, for obtaining photographs 

 of Nicolet's plates for me. 



