3. Parastephos pallidus, G. O. Sars. 

 (Pi. ill). 



Parastephos pallidus, G. O. Sars, Account of the Crustacea of Norway, Vol. IV, p. 65, Pi. XLIV. 



Specific Characters. Female. Body very slender, with the two chief 

 divisions sharply marked off from each other, the anterior one regularly oblong 

 oval in form. Cephalic segment with a faint transverse suture behind the 

 middle dorsally; front blunted, without any traces of rostral filaments. Last 

 truncal segment completely fused with the preceding one, and having the 

 lateral parts only slightly produced. Urosome very powerfully developed, 

 equalling in length about 2 /a of the anterior division, its 3 anterior segments 

 expanded behind to elevated circular ridges densely clothed with delicate 

 recurved spinules; genital segment scarcely at all protuberant below and, as 

 usual, the largest, though not much exceeding in size the succeeding segment; 

 anal segment well developed and of sub-cylindrical form; without any elevated 

 ridge behind. Caudal rami scarcely longer than they are broad; apical setae 

 slightly divergent, the innermost but one on left ramus remarkably produced, 

 being nearly twice as long as that on the right ramus. Anterior antennae of 

 the very same structure as in the male, and extending, when reflexed, to the 

 end of the genital segment. Posterior antennas and oral parts exactly as in 

 the male. Natatory legs of quite normal structure and resembling those in 

 the genus Stephos. Last pair of legs likewise built on the same type as in 

 that genus, but of comparatively much larger size and pronouncedly asym- 

 metrical, the left leg being considerably longer than the right; distal joint in 

 both legs conically produced and armed outside with a row of 12 15 coarse 

 denticles, the proximal of which is somewhat remote from the others and of 

 larger size. 



Body in the living animal semipellucid, of an uniform whitish grey 

 colour, without any obvious pigmentation. 



Length of adult female reaching to 2.20 mm. 



Remarks. Of this form, as above mentioned, only the male sex was 

 formerly observed by me. The female, as usual, is of considerably larger size, 

 and exhibits a most anomalous appearance by the powerful development and 

 peculiar armature of the urosome. The last pair of leg are also remarkable 

 by their comparatively large size, and more particularly by their conspicuous 

 asymmetry, also observed by Scott. Another asymmetry, not mentioned by 

 that author, is found in the extraordinary length of one of the caudal setae on 

 left side. On the other hand has the asymmetry described by the present 



