498 



The 2nd segment of pereopods I is straight; the 4th segment is 

 strongly broadened in the distal part; the 3rd and 4th segments are densely 

 pubescent, with fine setae, along the posterior margin; the anterior distal 

 angle of the 5th segment forms a small rounded process; the posterior 

 distal angle of the 5th segment is only slightly less than a right angle, 

 and its margins bear a few high teeth between which smaller denticles 

 may occur; the 6th segment also has a denticulate posterior margin; the 

 claw is strong but rather short. Pereopods II are longer than pair I; the 

 anterior angle of the 5th segment does not form a process while the pos- 

 terior one is more pointed and longer than in pereopods I but with similar 

 ornamentation. The 2nd segment of pereopods V is oval and almost half 

 403 the length of the distal segments together; the 2nd-5th segments are 

 armed with spines along the anterior and sometimes even the posterior 

 margin. Pereopods VI are equal in length to pair V; the 2nd segment is 

 approximately half the length of the distal segments together; the 4th-6th 

 segments have a denticulate anterior margin. Moreover, the 2nd-6th seg- 

 ments are armed with spines along the anterior margin and the 4th and 

 5th segments with lateral spines. Pereopods VII have a strongly broad- 

 ened 2nd segment in which the posterior margin is much more bulged 

 than the anterior; the distal segments together are somewhat shorter than 

 the 2nd segment. 



The first urosomite has bulged, the last urosomite concave lateral 

 margins; the last urosomite is half as long as its maximum width. The 

 endopodite of uropods I is 1 .5 times longer than the basipodite and both 

 rami extend beyond the telson by half their length. The endopodite of 

 uropods II is more than twice as long as the basipodite, the exopodite 

 shorter. The rami of uropods III are barely broadened in the middle part 

 and the endopodite extends over the tip of the telson by half its length. 

 The telson is roundish, slightly longer than wide, and equal in length to 

 the last urosomite. 



Distribution: Known from the Atlantic (50° N. to 6° S.), Indian 

 (8° N. to 12° S.), and Pacific (north of 40° S.) oceans. 



XXI. Family OXYCEPHALmAE Bate, 1861 



The external appearance of these crustaceans is unique and a vivid exam- 

 ple of adaptation to a purely pelagic mode of life. The integument is 

 thin, semitransparent or absolutely transparent, sometimes colored in 

 dull brown tones. The body is more or less elongated, cylindrical, or 

 laterally compressed, sometimes slightly bulged in the thoracic region 

 or strongly tapered. The head is stretched forward, its length (with the 

 rostrum) appreciably more than the width and height. In some cases the 

 head is demarcated from the body by a narrow neck. The eyes are very 



