553 



2nd segment, starting from the place of articulation of the 3rd segment, 

 is longer than the proximal part, but in males shorter; the distal segments 

 together are 1/4 the length of the 2nd segment; the 4th segment with its 

 distal process reaches 1/3 the length of the 5th segment. The 2nd segment 



445 of pereopods VII is bent forward and its length may be three-seven times 

 its width; the distal part of the pereopods consists of one-two short 

 rudimentary segments. 



The rami of uropods I and II are lanceolate, the endopodites some- 

 what longer than the exopodites. The endopodite of uropods III is fused 

 with the basipodite, its tip slightly extending beyond the tip of the telson; 

 the exopodite is half the length of the endopodite and much narrower 

 than it. 



Notes: Claus (1879b, 1887), Bovallius (1887a), and Spandl (1927) 

 placed this species in the genus Hemityphis (Dithyrus). However, a com- 

 parison of certain characters of the type species of the genera Platyscelus 

 and Hemityphis reveals an undisputable similarity between the described 

 species and the species of Platyscelus but significant differences from 

 the species of Hemityphis. Thus in pereopods I and II the margins of the 

 chelae are denticulate as in Platyscelus; the 3rd segment of pereopods V 

 is articulated with the 2nd segment submarginally as in Platyscelus and 

 not marginally as in Hemityphis; pereopods VII have one^;wo rudimen- 

 tary distal segments, which is characteristic of Platyscelus, whereas in 



446 Hemityphis these segments are absent. Finally, the shape of the head 

 (front view) is also the same as in Platyscelus, i.e., width considerably 

 more than length and rather large beak-shaped process in the ventral part; 

 in Hemityphis the height and width of the head are equal and the beak- 

 shaped process barely discernible. Based on the foregoing comparison, 

 retainig this species in the genus Platyscelus appears better justified. 



Distribution: Known from the Atlantic (equatorial region), Indian 

 (Zanzibar), and Pacific (Kuroshio) oceans. It is found in the upper 200 m 

 layer. 



2. Genus Hemityphis Claus, 1879 



Claus, 1879b: 4; 1887: 31; Stebbing, 1888: \A1\.— Dithyrus Bovallius, 

 1887: 46. 



The body is compact, the pereon bulged, and the head ventrally 

 terminates in a small beak-shaped process. The width and height of the 

 head are equal, unlike in species of the genus Platyscelus in which the 

 width is much greater than the height. The distal segments of antennae II 

 in males are more than half the length of the proximal segments. 



Pereopods I and II have chelae; the distal projection of the 5th seg- 

 ment of pereopods I is shorter than or equal to half the length of the 

 6th segment, in pereopods II only slightly extends beyond its middle; 



