494 



ones, with the basal joint slightly expanded. Last pair of uropoda rather 

 large, reaching considerably beyond the others, rami subequal, foliaceons and 

 edged with ciliated setae. Telson very small, bilobed. 



Remarks. — The present genus was established by Sp. Bate, to 

 include the arctic form described by Sabine as Gammariis loricafas. It is 

 chiefly distinguished by the distinctly carinated body, the strong rostral 

 projection, the peculiar structure of the gnathopoda, the greatly elongated 

 3rd and 4th pair of pereiopoda, and finally, by the structure of the last pair 

 of uropoda, and that of the telson. The 2 North American species, Gammarus 

 mucronatus Say and G. macyophthalmns Stimpson, which are referred by Sp. Bate 

 to this genus, should perhaps more properly be included in the genus Amathilla. 

 To the fauna of Norway belongs but a single species, which has formerly 

 been regarded as only a variety of the arctic form, G. loricatus. 



7. Gammaracanthus relictus, G. 0. Sars. 



(PI. 174). 



Gammaracanthus loricatus, Lov^n, Om nagra i Vennern och V'ettern funua Crustaceer. 



0fvers. af Kgl. Svenska Acad. Forbandl. f. 1861, p. 287. 



Body slender and compressed, with the dorsal keel rather low 

 anteriorly, scarcely forming any distinct projections in front of the 5th 

 segment of mesosome, dorsal projections of the succeeding segments not very 

 large, and terminating each in a very acute point, those of the first 2 

 segments of urosorae triangularly pointed. Cephalon (including the rostrum) 

 about the length of the first 3 segments of mesosome combined, and having 

 on each side, behind the lateral corner, a tuberculiform projection, rostrum 

 but very slightly curved, and not reaching to the end of the basal joint of 

 the superior antennae, lateral corners very small, rounded. Anterior pairs 

 of coxal plates not as deep as the body, oblong quadrangular in form, and 

 each provided with a longitudinal ridge; 5th and Gth pairs with the lobes 

 triangularly pointed, those of the former pair somewhat unequal, the anterior 

 one being the larger, and nearly as deep as the preceding pair Last pair 

 of epimeral plates of metasome scarcely produced at the lateral corners, being 

 nearly rectangular. Eyes comparatively small, rounded, pigment dark. 

 Superior antennae nearly half as long as the body, joints of the peduiude 

 successively decreasing in size, flagellum somewhat longer than the peduncle, 

 and composed of about 22 articulations, accessory appendage about the length 

 of the last peduncular joint, and 4-articulate. Inferior antennae scarcely more 

 than half as long as the superior and much narrower, their basal joint being 

 however much swollen and subglobose in form, last joint of the peduncle 



