1873.] Genus of Amphipod Crustaceans, 207 



Thaumops pellueida, n. sp. 

 Corpus longitudine 14 mm., latitudine 21 mm., pellucid uui. 



An anatomical description of this interesting animal is given, illustrated 

 by two plates ; and it is shown that, among the Amphipods known to us, 

 Phronima is its nearest relation. But there are so many points in which 

 this genus differs from Phronima, that it cannot form a member of the 

 family Phronimidae ; and I therefore propose to establish for it a new 

 family, Thaumopidae, belonging to the tribe of Hyperina. 



The form of the head is totally different from that of Phronima ; the 

 antennae are not situated near the mouth, but at its front, and the 

 enormous faceted eyes occupy its upper surface. The first two pairs of 

 thoracic appendages are not, as in Phronima, ambulatory legs, but 

 maxillipeds, so that only five pairs of legs are ambulatory in Thaumops. 

 The thorax is composed of six segments — the first of which has, on its 

 underside, the vulva and one pair of maxillipeds ; and the second, re- 

 presenting two segments, bears two pairs of appendages, the larger 

 maxilliped and the first pair of ambulatory legs. The abdomen consists 

 of five segments, with three pairs of pedes spurii, the caudal appendages 

 being attached to the fourth and fifth segments. 



The animal being beautifully transparent, the nervous system could be 

 carefully worked out without dissecting it ; the position of the nerves 

 going out from the cephalic ganglion, as well as that of the five pairs of 

 thoracic and the three pairs of abdominal ganglia, could be ascertained. 

 The eyes, having at their borders very peculiar appendages, were examined, 

 and a description is given of the structure of the large crystalline bodies 

 which are to be seen in them. Organs of hearing and touch have not 

 been discovered. 



The mouth is covered by a pair of maxillae and a small labium. There 

 is a recurved oesophageal passage leading into a large caecal stomach, 

 and an intestinal tube departing from near the end of the oesophagus and 

 running straight to the anus. 



The heart is an elongated tube extending from the second to the fifth 

 segment, with probably three openings. Three pairs of transparent sac- 

 like gills are attached at the base of the second, third, and fourth pairs of 

 feet. 



Genital organs. — The single specimen taken is a female. The Ovary, 

 probably composed of two ovaries, has a rose-colour, and the genital 

 papilla is situated at the under part of the first segment ; it is covered 

 by two small lamellae, which in this case did not sustain the eggs, which 

 were found to be attached to the first pair of ambulatory legs. The 

 animal seems to carry them in a manner similar to the pycnogonid 

 JSfymphon. 



Development. — The eggs contained embryos having already the antenna?, 



