Cuitton.—Some New Zealand Amphipoda. 631 
Some New Zealand Amphipoda: No. 5.* 
By Cuas. ©нптох, M.A., D.Sc., LL.D., &e., Professor of Biology, Canter- 
bury College, ie Zealand. 
[Read before the Philosophical Institute of Canterbury, 5th December, 1923 ; received by 
Editor, 28th кие) 1923 ; issued separately, 28th August, 1924.] 
Tetradeion crassum (Chilton). (Figs. 1 to 20.) 
scher dien Chilton, 1883, Trans. N.Z. Inst., vol. 15, p. 80, 
pl. 3, fig. 1.  Tetradeion sp. typ. Stebbing, 1899, Ann. Mag. 
Nat Hist, ser. 7, vol. 4, p. 207. — Tetradeion crassum Stebbing, 
1906, “ Das Tierreich ” Amphipoda, p. 157. 
The original description of this species, drawn up in 1883, was based 
on two specimens only, the sm уе of which, probably immature, was 
issected. Since then numerous other specimens have been obtained 
imm Lyttelton and other oos dí, and a fuller description is desirable, 
ince the original account, though accurate enough as far as it goes, was 
dados in cm it contained no reference to the mouth-parts and an 
important character—viz., the reduced condition of the fifth peraeopod— 
was overlooked. 
e species was provisionally placed under the genus Cyproidia 
Haswell, though it was pointed out at the time that it differed very 
considerably in the character of the side-plates. In this respect the 
арена approaches closely to Stegocephalus and allied genera, but descrip- 
ns and figures of these were not available in New Zealand at the time. 
B "1899 Stebbing established the genus Tetradeion for the species, and gave 
the following diagnosis based on the original description :— 
“ Body short and stout, pleon shorter than peraeon. Head small, 
rostrum obsolete. Side-plates 1 to 4 together forming a continuous shield, 
the confronted margins E the contiguous side-plates neatly fitting, fourth 
much broader — first to third combined, fifth much broader than deep, 
fitting hind. J 
well developed. гу тч пае 1 and 2 small. vmi 1 the stouter, ‘without 
accessory flagellum. nt i b "der rope joint of peduncle shorter 
than antepenultimate. Mou rts unknown. Gnathopods 1 and 2 
equal, similar, _imperfeetly ра fourth and fifth joints slightly 
produced. Peraeopods 1-5 slender, character of second joint unknown, 
far back as uropod 1, rami a little unequal. Uropod З reaching so far 
back as the other pairs, stouter, rami туи одне Telson entire, 
oval, short 
To this must be added a note on the mouth-parts, which prove to be 
very similar to those of Phippsia gibbosa (Sars), and to the fact that the 
* Previous numbers of this series have appeared in Trans. N.Z. Inst. as follows : 
No. 1, vol. 52, p. 1; No. 2, vol. 53, p. 220; No. 3, vol. 54, p. 240; No. 4, vol. 55, p. 269. 
