STEBBING— ISOPODA 1 1 5 



Sars. His species, A. simplex, is parasitic on Boreomysis arctica (Kroyer), and he remarks 

 that in all instances of its capture " the marsupial pouch of the host was fully developed, 

 and it thus seems that the parasite must have entered the pouch immediately after the 

 young of the host had escaped : several male specimens were found with the female, and 

 in one instance two or three females of different development were found in the same 

 host" (Crustacea of Norway, vol. ii., pp. 233, 238, 1899). It seems possible that in these 

 cases the marsupial plates develop round the parasite which usurps the place of eggs. In 

 the tube with the Trapezicepon there were no eggs, but a Bopyrus-form which I have 

 regarded as the male of T. amicorum, and, in addition to this, four specimens of a 

 cryptoniscian larva, slightly larger than the Bopyrus-form, not very greatly differing from 

 the male of Asconiscus simplex as figured by Sars. There was also present a very much 

 smaller cryptoniscian larva, and a very small duplicate of the bladder-like organism. The 

 relative sizes of these creatures may be judged from the plate, wherein they are drawn to 

 the same scale. If I am right in supposing that the specimens which have lost all clear 

 traces of segmentation belong to Asconiscus or some closely allied genus, it will be, 

 I believe, a novelty to find one of the Epicaridea parasitic on one of its own tribe, though 

 there are well-known instances of Epicaridea parasitic on other parasites. Zeuxo 

 longicollis, described by Kossmann in his Zool. Ergebnisse einer Reise in die Kustenge- 

 biete des rothen Meeres, first part of second half, p. 124 (1880), as figured in his pi. 11, 

 fig. 8, is very like in shape to the occupant of our Trapezicepon s marsupium, but with a 

 comparatively long " tap-root " instead of a short one. 



Gen. ERGYNE, Risso. 



1816. Ergyne, Risso, Crustaces des environs de Nice, p. 150. 



1887. Portunicepon, Giard and Bonnier, Travaux Lab. Zool. Wimereux, vol. v., 

 p. 73. 



1893. Ergyne, Stebbing, History of Crustacea, Internat. Sci. Ser., vol. lxxiv., p. 413. 



1900. Portunicepon, Bonnier, Les Bopyridse, p. 270. 



The hind lamina of the head has at the outer corners two simple lappets. The 

 perseon carries medio-dorsal bosses. The inner branches of the pleopods are more or less 

 lobed, like the outer branches and the lateral extensions of the segments. 



Risso's original species, E. cervicornis, was transferred to Cepon by Kossmann in 

 1881. The species of the genus may be distinguished as follows: 



Sixth and seventh segments of perseon raised into median bosses. 1. E. hendersoni 

 (Giard and Bonnier). 



Fifth, sixth and seventh segments so raised. 2. E. cervicornis, Risso. 



A slight carina rising from the first segment to strongly developed bosses on the 

 last three. 3. E. savignyi, n. sp. 



31. Ergyne savignyi, n. sp. (Plate 10 a.) 



Female. Head very broad; in the hind lamina the outer lappet is much longer than 

 the inner, both are microscopically beset with minute setules. The centre of the peraeon 

 is slightly angled on the first three segments, more decidedly on the fourth, while each of 



L5— 2 



