53 



prominent wing-like expansions in some instances divided into sol't filiform 

 processes; that of male simple cylindric, without any dorsal expansions. 

 Incubatory pouch of moderate size and more or less produced at the end. 

 Tail composed in both sexes of 4 segments, the last of which is simple, truncate 

 at the end. Caudal rami forming 2 compressed pieces curving downwards 

 and each armed on the narrowly truncated end with 4 subequal hooks. An- 

 terior antennae alike in the 2 sexes, and comparatively more slender than in 

 Pachypygus. Posterior antennae and oral parts built on a similar type to that 

 in the said genus. The 4 anterior pairs of legs however conspicuously dif- 

 fering in the structure of the inner ramus, which in all the pairs is only com- 

 posed of 2 joints. Last pair of legs comparatively small with the distal joint 

 narrow linear in form. 



Remarks. This genus was established as early as the year 1852 by Costa, 

 and is chiefly characterised by the peculiar wing-like expansions of the free 

 trunkal segments in the female, these expansions attaining in some instances 

 quite an extraordinary development. Otherwise it comes very near to the 

 genus Pachypygus, yet differing from it also somewhat in the structure of the 

 legs and that of the caudal rami. Several species of this genus have been 

 recorded by different authors, and chiefly distinguished by the different deve- 

 lopment of the above-mentioned expansions. As however these expansions 

 appear to be subjected to some variation, the limits between the several species 

 are not always easy to fix exactly. Three Norwegian species referable to this 

 genus will be described below. 



15. Notopterophorus auritus, (Thorell). 



(PI. XXVI) 

 Doropygus auritus, Thorell, 1. c. p. 50, II. VII, PI. VIII, 10. 



Specific Characters. Female. Body moderately slender and gently curved, 

 with the free segments of trunk sharply defined by deep constrictions; wing- 

 like expansions only slightly prominent and quite evenly rounded at the end, 

 those of 1st segment confluent, the others well defined, though contiguous at 

 the base anteriorly. Incubatory pouch not very large, irregularly quadrangular 

 in outline, and terminating behind in an obtuse point. Tail about half the 

 length of the anterior division, and slightly tapering distally, with the last 

 segment the smallest. Caudal rami slightly curved and gradually attenuated 

 distally, with a small bristle somewhat beyond the middle of the upper edge; 

 tip narrowly truncated and armed with 4 hooks of equal size. Anterior an- 



