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XVII. On a new Genus of Amphipod Crustaceans. By Kudolph von Willemoes- 
Suhm, Ph.I)., Naturalist to the ‘ Challenger ’ Exploring-Expedition. Communicated 
by Dr. Wyville Thomson. 
Received February 27, — Read March 6, 1873. 
Leaving Gibraltar on the 26th of January, 1873, H.M.S. ‘ Challenger’ proceeded in a 
south-westerly direction, and on the 28th the trawl was sent down, in lat. 35° 47', long. 
8° 23', to a depth of 1090 fathoms, the temperature of the surface being 15 0, 55 C., and 
that of the bottom 2 0, 66 C. The haul was an uncommonly rich one ; for, besides three 
species of fishes and many very interesting Echinoderms, a species of Euplectella was 
brought up and a large transparent animal, which we at first thought might be the larva 
of one of the higher Crustaceans. 
Two enormous faceted eyes occupying the whole upper part of the head, and the 
presence of what seemed clearly to be an ovary, negatived, however, that supposition ; 
and at Professor Wyville Thomson’s request I made a closer examination of this 
animal, which was evidently of great interest in many respects. 
The specimen is almost entirely transparent. Its length is 84 millims. and its 
greatest breadth 21 millims. The body consists of three parts : — 1. The head, with one 
pair of antennae in front, two contiguous faceted eyes occupying the whole of its upper 
surface, and the mouth situated at the posterior part of the under surface. 2. The 
thoracic region , composed of six segments, bearing two pairs of maxillipeds, five pairs 
of ambulatory legs, and three pairs of branchiae. The second pair of maxillipeds and 
the first pair of ambulatory legs are on the second thoracic segment, which, as we shall 
see hereafter, may probably be formed by the fusion of two segments. We also 
remark the vulva on the under surface of the first segment. 3. The abdomen , 
which consists of five segments, three bearing pairs of pedes spurii, and the fourth 
and fifth the caudal appendages and the anus. An elevated line running along the 
dorsal aspect of the thoracic and abdominal regions divides them longitudinally into a 
right and a left half. 
The Head. — The upper surface of the head is entirely occupied by two contiguous 
faceted eyes, which are separated from one another by a mesial line, 20 millims. in 
length (Plate XLIX. figs. 2 & 3). Each eye is 13 millims. in width, and its anterior 
and lateral borders are limited by a slightly coloured band, which will be referred to 
when considering the structure of the eyes. The posterior border nearly corresponds 
with the posterior border of the head, which arches gently over to the first segment of 
the thoracic region. The anterior border of the head is transverse and nearly straight, 
4 P 2 
