178 



wards, frontal lobe less prominent, and broadly rounded. Side-plates of meso- 

 some well developed, with the posterior corners acuminate. Metasome scarcely 

 attaining 1 / 4 , of the length of the body, epimeral plates of 3rd to 5th segments 

 prominent, recurved; last segment considerably produced, being almost as long 

 as it is broad at the base, terminal part acute and slightly grooved above. An- 

 tenna? rather slender, nearly half as long as the body, 2nd and 3rd joints of 

 the peduncle carinated outside, the carina being in each of the joints produced 

 at the end to a dentiform projection; flagellum not attaining the length of the 

 last peduncular joint, and having its proximal articulation nearly twice as long 

 as the distal one. Last pair of legs in male more strongly built than in female, 

 with the carpal joint considerably dilated. Opercular plates of the 2 anterior 

 pairs of pleopoda with very distinct air-cavities. Uropoda with the outer ramus 

 rather broad, and considerably larger in male than in female. Colour of dorsal 

 face yellowish grey, variegated with dark brown patches, which are generally ar- 

 ranged in 5 longitudinal series on the mesosome, cephalon and middle part of 

 metasome uniformly blackish. In fresh specimens, moreover, a double row of 

 very conspicuous light yellow patches occurs along the middle of the mesosome, 

 caused by some opaque matter lying beneath the skin (renal excretions). Length 

 of adult female reaching to 14 mm. 



Remarks. The present species may be easily recognized by the compa- 

 ratively greatly depressed body, the broadly rounded frontal lobe, the slender 

 antennae, and the peculiar colouring of the dorsal face. In fresh specimens, the 

 above-mentioned opaque patches along the dorsal face of the mesosome are very 

 conspicuous, and may at once suffice for distinguishing this species from its allies. 

 The extent of the dark patches is, on the other hand, rather variable ; but in all 

 the specimens the cephalon and the middle part of the metasome exhibit a 

 uniformly dark colour, and this has, indeed, given rise to the specific name, me- 

 hmocephalus, proposed by Koch for this species. 



Occurrence. In the vicinity of Christiania this form is by no means un- 

 common, occurring in some places rather abundantly beneath stones and pieces 

 of wood, and I have also received specimens collected by conservator Storm at 

 Trondhjem. It is not uncommonly found in rather dry situations, where no other 

 Oniscoid seems to thrive. It is very agile, running about with great rapidity 

 when disturbed, and is thus only to be got hold of with difficulty. 



Distribution. Sweden, Denmark, Germany, Britain, France, Hungary, 

 Russia, North America. 



