In young males of Hyale grandicornis, and perhaps of other species, the carpus of the second gnathopod is produced into a process lying between the merus and propod, similar to the one normally found in adult males of Allorchestes. This process is also present in the females of both genera; in many cases it cannot be demonstrated without dissction of the appendage, and its value as a generic character is accordingly reduced. The shape of the telson differs in the two genera, but this character again is one that is not always readily observed. Fig. 4.—Allorchestes novizealandiae Dana: female. a, first gnathopod; b, second gnathopod. It is not surprising, therefore, that the identifications of Allorchestes novizealandiae made up to the present are somewhat uncertain. Fortunately I am able to give below a distinguishing character which is, I think, quite reliable, though it is well marked only in adult males. Allorchestes novizealandiae Dana. Allorchestes novizealandiae Dana, 1853 and 1855, p. 894, pl. 61, fig. 1 a–f (male), g–v (female). Allorchestes novizealandiae Stebbing, 1906, p. 581 (with synonyms). Hyale chiltoni G. M. Thomson, 1899, p. 206. This species was described and very fully figured by Dana in 1852, and, though it has been referred to by both Mr. G. M. Thomson and myself