Crustacea.] 



SUBANTARCTIC ISLANDS OF NEW ZEALAND. 



667 



13 a 



Fig. 19. — Deto aucldandiae (G. M. Thomson). 



19a. Male (dorsal view) ; X 2. 

 196. Female (dorsal view) ; x 2. 



fig. 2, 1901. Deto magnifica, Budde-Lund, Deutsche Siid-polar Exped., 

 ix, p. 86, 1906. D. robusta, Budde-Lund, I.e., p. 87, pi. iv, figs. 42-44, 

 1906. D. aucMandiae, Budde-Lund, I.e., p. 87 ; Chilton, Trans. N.Z. 

 Inst., xxxviii, p. 273, 1906. 



Several specimens of this species were obtained on previous occasions at Ewing 

 Island, in the Auckland Group, but unfortunately no additional specimens were 

 collected during the expedition. It is a 

 very large and handsome species, reaching 

 a length of 23 mm., and it shows very 

 marked sexual dimorphism, the male (fig. 

 19a) differing from the female (fig. 196) in 

 the greater development of tubercles on the 

 dorsal surface and particularly in the size 

 and thickness of the external antennae. 

 These are very massive, and have the 

 various joints fully twice as broad as those 

 of the female ; they have been figured by 

 Budde-Lund under the name D. robusta. 

 The joints of the flagellum, and to some 

 extent also the terminal joints of the pe- 

 duncle, are thickly covered with a fine 

 down of short setae. In the male, too, the 

 tubercles on the dorsal surface are much 



better marked than in the female ; each segment bears a row of about ten to 

 twelve tubercles, the lateral ones being longer than those in the centre, and pro- 

 jecting up from the dorsal surface like short blunt spines* ; in the pleon they are 

 much shorter, and form slight tubercles only, similar to those found on the dorsal 

 surface of the peraeon in the female. 



When preparing my paper on the terrestrial Isopoda of New Zealand, quoted 

 above, I had only a single female specimen of this species, and the male then 

 remained unknown. There are three dried specimens of this species, from Auck- 

 land Island (one of them imperfect), in the Dresden Museum ; these were examined 

 by Budde-Lund, who has described them as forming two new species, D. magnifica 

 and D. robusta, though he stated that the first, one was perhaps not distinct from 

 D. aucMandiae. I have no doubt that bothl^of his species must be referred to 

 D. aucMandiae, his description of D. robusta being evidently based mainly on the 

 examination of a male specimen, and agreeing closely with the male specimens in 

 my collection. 



I had formerly considered Oniscus novae-zealandiae, Filhol, as a doubtful syno- 

 nym of D. aucMandiae, but specimens since received from the Chatham Islands 

 and from Stewart Island show that it is a distinct species, and must therefore be 

 known as Deto novae-zealandiae. It differs from D. aucMandiae in the secondary 

 sexual characters, for the male has the lateral portions of the first segment of the 

 peraeon dilated into two bladder -like structures. A female specimen belonging 



* These are much longer than is shown in fig. 19a. 



