1078 THE VOYAGE OF H.M.S. CHALLENGER. 



on the surface nearer the front, the finger has its inner margin cut into eleven denticles, 

 and the long sharp nail curves across the palmar spine beyond the obliquely convex 

 finely pectinate palm, so as to become parallel with the hind margin. In the second and 

 smaller gnathopods, the long spines of the third joint cross the surface at an angle with 

 the distal margin ; the spines along the serrate hind margin of the wrist and hand are 

 more numerous and closely set than in the first gnathopods, the hand is oblong, rather 

 longer than the wrist, the palm is only slightly oblique, and the short finger fits it, its 

 tip when closed only just appearing beyond the spine which defines the palm ; the inner 

 margin of the finger is cut into small teeth ; the spines on the surface and front margin 

 of both wrist and hand are nearly as in the first gnathopods. 



The peraeopods seem to agree in shape and proportion with those of the males above 

 described, and in particular the fifth joint of the second perseopod showed the same 

 armature as that figured for the male, prp>.\. A., differing from that of prp.l. C. the 

 female, as I suppose, of the other species. The great size of the finger in the fifth 

 perseopods may also be noticed as a distinguishing characteristic. 



Locality. — The specimen came from Kerguelen Island, the depth not specified. The 

 figure of the upper antenna and part of the lower in the Plate, a.s. D., was drawn from 

 a female specimen which seems to belong to this species, a specimen also taken at 

 Kerguelen, and labelled as coming from a depth of 120 fathoms. 



Aora trichobostrychus, n. sp. (PI. CIX. figs. B. $ , C. ? ). 



The resemblances between the species of the genus Aora as yet described are so great 

 as to suggest the possibility of their in fact constituting but a single true species, widely 

 distributed, and subject to local variation. 1 The difference between male and female in 

 this genus is sufficiently well known, and it is easily understood that there will be 

 variations in the form of the male according to its age, while there is the further 

 possibility that even the adult male may show some variety of form. The probability 

 that the different specimens of Aora from Kerguelen Island all belonged to a single 

 species, induced me to figure on a single Plate parts of different specimens which showed 

 variation, and it was not till I had written most of the description, including all the 

 specimens under one species, that the complication of the narrative brought me to a halt. 

 Upon carefully reviewing the different characteristics, I at length came to the conclusion 

 that less confusion was likely to arise from giving two names to one species, if so it 

 should eventually prove, than by describing two distinct species under one and the same 

 name. The following description is intended chiefly to bring out the points of distinction, 

 real or supposed, between this species and Aora kergueleni. 



Upper Antennas. — First joint long, slightly curved, moderately thick, with some 

 slender spines at the apex ; the second joint longer and much thinner, also slightly 



1 See especially Mr. Chilton's paper, Ann. and Mag. Nat. Hist., ser. 5, vol. xvi. p. 369. 



