TAISTAIDACEA AND ISOPODA— TATTERSALL. 217 



male except for the outer ramus, which is strongly hooked at the outer distal 

 extremity. 



Antennule (pi. V, fig. 3) very slightly longer than the head ; first joint of the 

 peduncle stouter and longer than the other joints, about twice as long as wide ; 

 second joint shorter than the third, latter not much more than half as long as the 

 first ; flagellum shorter than the peduncle, seven -jointed. 



. Antenna (pi. V, fig. 4) longer than the antennule, but not quite reaching the 

 posterior end of the first somite of the thorax ; flagellum a little longer than the 

 peduncle, thirteen-jointed. 



Second to the eighth thoracic limbs (pi. V, figs. 5-6) long and slender, progres- 

 sively increasing in length from the second to the seventh pair, mainly by the increase 

 in length of the meral and especially of the carpal joints ; in the second limbs, the 

 carpus is quite small and the merus hardly longer than wide, while in the eighth pair 

 the carpus is not much shorter than the propodus and equal to the merus ; the limbs 

 have a varying armature of long setae, especially from the outer distal corner of the 

 meral joints, and the inner margin of the merus and carpus of the posterior limbs has a 

 dense fringe of short setae. 



Male stylet on the second pleopod of the male (pi. V, fig. 7) rather more than 

 twice as long as the rami, rather sharply curved towards the finely pointed apex. 



Length of male and female types, 2 ■ 5 mm. Across the head and first somite of 

 the thorax, and also across the last somite of the thorax and anterior somite of the 

 abdomen, are two bands of dark purple pigment. 



This small species may be distinguished by the smooth body, the shape of the outer 

 ramus of the uropods in both sexes, and the long dorsally recurved epistome, giving a 

 snub-nosed effect in latei'al view. 



Genus ISOCLADUS, Miers, 1876. - 

 26. Isodadus armatus (Milne-Edw.). PL V, figs. 9-17. 



Sphaeroma armata, M.-Edw., 1840, p. 210; Dana, 1852, p. 780, pi. LII, fig. 7. 



Isodadus armatus, Miers, 1876(1), p. 229 ; Miers, 1876(2), p. 112; Thomson and Chiltoo, 



. 1886, p. 155 ; Hansen, 1905 (1), p. 118 ; Thomson, 1913, p. 246. 

 Sphaeroma spinigera, Dana, 1852, p. 780, pi. LII, fig. 8. 



Isodadus spiniger, Miers, 1876 (1), p. 229 ; Miers, 1876 (2), p. 113, pi. Ill, fig. 4 ; Thomson 

 and Chilton, 1886, p. 155 ; Hansen, 1905 (1), p. 118 ; Thomson, 1913, p. 246. 



Occurrence. — Sandy pool between tide marks at Motorua, Bay of Islands, New 

 Zealand, sixteen males and nine females. 



Remarks. — I have figured (pi. V, figs. 9-11) the adult male, adult female and 

 young male of this species, to show the sexual differences and the changes in the 

 growth of the young male to fully adult size, and to support my contention that 

 /. armatus and I. sjjiniger are really different sexes and growth-stages of the one 

 species, which I regard as the Sjyhaenvna armata of Milne-Edwards. 



2 I 2 



