121 



slender, with the peduncle 5-articulate, and the flagellum well developed. Man- 

 dibles of a similar structure to that in the genus Nannoniscus, but without any 

 trace of palp. Maxillipeds with the 2 outer joints of the palp rudimentary. Legs 

 rather unequal; the 2 anterior pairs of essentially the same structure, not .prehensile; 

 3rd pair much more strongly built, and apparently fossorial in character; the 

 4 posterior pairs very slender and rapidly increasing in length. Female oper- 

 culum very narrow ; male operculum transformed in the usual manner. Uropoda 

 very slender, styliform, simple, bi-articulate and greatly divergent. 



HemarJcs. — This genus was established by the present author as early as 

 in the year 1863, to include a very peculiar, small Isopod from the Christiania 

 Fjord. The genus Vana of Meinert is unquestionably identical with the present 

 genus. In the structure of the legs and uropoda, this genus differs rather con- 

 spicuously from the other Desmosomidce, though it evidently ought to be referred 

 to that family. Only a single species is as yet known. 



Macrostylis spinifera, G. 0. Sars. 



(PI. LI.) 



Macrostt/lis spiinfcra, G. O. Sars, Om en anomal Gruppe af Isopoder. Chr. Vid. Selsk. Forkandl. 



1863, p. 15. 



Syn: Vana longiremis, Mainert. 



Specific Characters. — Body oblong, semicylindric in form, being more than 

 4 times as long as it is broad. Cephalon rather broad at the base, and very 

 slightly sinuated on each side for the insertion of the antennae, frontal part con- 

 siderably produced, and obtusely rounded at the tip. The 4 anterior segments of 

 mesosome with the lateral parts scarcely at all expanded; 3rd segment the lar- 

 gest; 4th segment terminating on each side in a posteriorly-pointing spine. The 

 3 posterior segments of mesosome much narrower than the anterior, and sepa- 

 rated by deep constrictions, lateral parts obliquely expanded, and terminating in a 

 short pointed projection. All the segments of mesosome, except the 1st, produced 

 ventrally to strong spiniform processes. Caudal segment nearly as long as the 3 

 posterior segments of mesosome combined, oblong pyriform in shape, with a slight 

 notch on each side, at some distance from the tip, the latter obtusely produced. 

 Superior antennae scarcely extending beyond the frontal part of the head, 4-arti- 

 culate, the last articulation representing the rudimentary flagellum. Inferior an- 

 tennae, when reflexed, extending about to the end of the 4th segment of mesosome, 

 penultimate peduncular joint the longest, flagellum shorter than the peduncle, and 

 7-articulate. 1st pair of legs of nearly exactly the same structure as the 2nd, 

 though having the carpus comparatively shorter; 3rd pair much more strongly 

 built, and generally extending laterally, ischial joint produced outside, beyond the 



1G — Crustacea. 



