440 6. 0. SARS, 



is of very considerable size, though not nearly as large as the arctic 

 species. 



The body (see tig. 1) exhibits the form characteristic of the genus, being 

 somewhat slender, and distinctly cariuated both dorsally and laterally. 



The dorsal expansions in this form, unlike what is the case in G. relic- 

 tus, are well defined also in the anterior segments of the raesosome, though 

 here somewhat lower than in the posterior segments. That of the 1st seg- 

 ment is evenly rounded, whereas the others are triangular and, especially 

 on the mctasome, sharply pointed. The expansions of the 2 anterior segments 

 (jf the urosome even assume a spinifonn character. The lateral keels are dis- 

 tinct throughout the whole mesosorae and metasome, and are even continued 

 along the sides of the 1st segment of the urosome. 



The cephalon is produced in front to a rather long, sharply -pointed 

 rostrum, which, however, is but very slightly curved, and does not extend 

 beyond the basal joint of the superior antennae. In the arctic species the 

 rostrum is much stronger, whereas in G. relidus it does not extend nearly 

 to the end of the basal joint of the superior antennae. Tlie lateral lobes are 

 scarcely at all produced, and are quite evenly ri)unded. Behind them, there 

 is on each side of the head a small umboniform protuberance. 



The anterior pairs of coxal plates are a little deeper than the correspond- 

 ing segments, and oblong quadrangular in form, with an obtuse keel running 

 along their outer face. They successively increase in size posteriorly, the 

 4th pair being nearly .3 times as large as the 1st, and having the posterior 

 edge slightly concave. 



Of the posterior pairs of coxal plates, the last one is quite simple, 

 whereas the 2 anterior pairs are each divided into 2 triangular lappets. In 

 the antepenultimate pair the anterior lappet is very large, being almost as 

 deep as the preceding pair. 



The epimeral plates of the metasome are rather large, and all of them 

 produced at the lateral corners to an acute point. 



The urosome is of moderate size, and has the last segment quite simple, 

 whereas the 2 anterior ones, as above stated, are elevated to strong, almost 

 spiniform dorsal expansions. 



The eyes are oval reniform in shape, having anteriorly a distinct sinus, 

 not found in G. relicfus. The pigment is very dark. 



The superior antennae are rather slender, and only clothed with very 

 small hairs. They somewhat exceed in length '4 ''f the body, and have the 

 peduncle rather elongated, though considerably sliorter than the flagellum, 

 which latter is divided into numerous short articulations. The accessory ap- 



'I'ua. -Jl.iT. CTp. 270. 20 



