390 Royal Societi/: — 



Thaumops, nov. gen. 



Caput oblonguin, inflatum, ociilis maximis superiorein capitis par- 

 tem tegentibus. Segmenta thoracica 6, abdomiualia 5. Anten- 

 narum in feminis par unum, maxillarum par iinum, pedum 

 paria duo minima maxillarum locum tenentia. Mandibulae 

 nullse. Pedes thoracici 5, abdominales 3 in utroque latere. 

 Appendices caudales 4. Gangliorum pectoralium paria 5, 

 abdominalium 3. 



Thaumops pellucida, n. sp. 

 Corpus longitudine 14 mm., latitudine 21 mm., pellucidum. 



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 relative. But 

 there are so many points m which this genus differs from Phronima, 

 that it cannot form a member of the family Phronimidse ; and 

 I therefore propose to establish for it a new family, Thaumopida), 

 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 maxillineds ; and the second, representing t\^•o 

 segments, bears two pairs of appendages, the larger maxillipeds 

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

 five segments, with three pairs of pedes spurii, the caudal appen- 

 dages being attaclied 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 w'hich 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 intestmal tube departing from near the end 

 of the esophagus 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 on/ans. — The single specimen taken is a female. The 

 ovary, probably composed of two ovaries, has a rose-colour ; and 



