50 G. O. Sårs. 



the usual longitudinal striæ, lower edges of valves minutely 

 setiferous. Ocellus rather large, though a little smaller than 

 the eye, and placed somewhat nearer to it than to the tip 

 of the rostrum. Antennulæ and antennæ of normal appear- 

 ance. Lip-plate large and evenly curved below. Caudal part 

 rather strongly built, and somewhat narrowed distally, dorsal 

 edge below the anal orifice very slightly curved, and armed 

 on each side with about 10 strong denticles, lateral denticles 

 absent, supra-anal projection well marked, lower corner some- 

 what produced and narrowly rounded, caudal claws strong, 

 with a well-marked denticle at the base. — Male some- 

 what smaller than female, with the head more erect, and the 

 carapace slightly widening behind. Caudal part very unlike 

 that of female, conical in form, gradually tapering distally, 

 supra-anal projection obsolete, marginal denticles much re- 

 duced, caudal claws rather small, spermatic ducts prolonged 

 in front of the latter to 2 digitiform processes. Colour 

 pale yellowish. Length of adult female 0.42 mm., of male 

 0.34 mm. 



Remarks. — In external appearnace, as also partly 

 in the structure of the caudal part, this form somewhat 

 recalls the European species, A. costata G. O. Sars. It is, 

 however, prominently distinguished by the entire absence of 

 the striæ of the carapace, so strongly marked in the Euro- 

 pean species. The caudal part (see fig. 2 a), though of a rather 

 similar form, is comparatively more strongly built, and the 

 marginal denticles are much coarser and fewer in number. In 

 the male this part (fig. 2 c) is transformed in a manner very 

 similar to that in the European species, the spermatic ducts 

 in both being prolonged beyond the tip, in front of the 

 caudal claws; but whereas in the European species, accord- 

 ing to Prof. Lilljeborg, only a single such apical papilla 



