270 



DISCOVERY REPORTS 



lost, and there is a discrepancy as regards the mandible (Stephensen, 1918, pp. 59, 60, 

 footnote) we cannot correlate any of the more adequately known species with it. 



Further, we may note that all four specimens with the antennae considerably longer 

 than the head are males (" longipes" B ; parkinsoni ' Challenger' F, and ' Thor ' 72 ; and 

 latipes), and that the linear outer rami of the uropods, which are longer than the inner 

 rami, have only been found in fully adult females of pellucidum, with the exception of 

 somewhat similar rami in the male "longipes" B. 



In the character of the mandibular spines and the ventral spines we find an almost 

 perfect sequence of numbers, thus : 



Mandibular spines : 



? 1 or 2 or rudimentary ... ... ... ... ... ... ... ... loveni 



1 



2 



3 



Number unknown 



Ventral spines : 

 ? 1 pair 



2 pairs 



3 .. 



4 » 



5 - 

 5-6 „ 



6 „ 



5-7 .. 

 8 „ 

 Number unknown 



fabricii, pellucidum, magnum, parkinsoni 



longipes, bovallii, latipes 



africaman 



coalition, " spinosum", neptunus 



... loveni 



fabricii, coalition 



... no specimen known 



two Discovery specimens 



.. magnum (Woltereck's specimens), "longipes" B 



longipes, latipes 

 ..africanum, parkinsoni ('Thor') magnum (Spandl) 



pellucidum 



neptunus 



bovallii, parkinsoni (' Challenger ' F) 



One can thus realize how difficult it is to define the species, especially when one re- 

 members that scarcely a dozen specimens of pellucidum have been adequately described, 

 and of the other "species" considerably fewer. 



Lastly, we may note that on one occasion the 'Valdivia' took i(J, 1? magnum and 

 1 $ fabricii in one and the same haul. The ' Gauss' took 1 ? magnum, 1 9 pellucidum and 

 1 immature specimen in one haul. The 'Discovery' has taken 1 $ pellucidum together 

 with 5 fabricii (2 ??, 3 juv.); on another occasion 1 immature pellucidum together 

 with 2 immature fabricii; and on another occasion 1 $ fabricii together with 1 immature 

 pellucidum. In one small area in the North Atlantic, measuring io° of latitude by 5 of 

 longitude, the ' Thor ' took three specimens of one species together with one each of 

 four other species. 



We may perhaps define the following species : 



fabricii, Stebb. 1 mand. spine ; 2 pairs ventr. spines ; antennae arising close together, about 



equal to length of head. 

 coalition (Wolt). Mand. spine ?; 2 pairs ventr. spines; antennae close together, about equal 



to length of head; segments 1-4 fused. (Possibly to be united with fabricii.) 

 pellucidum (W. Suhm). 1 mand. spine; (4) 5-6 (7) pairs ventr. spines; antennae arising far 



apart, about equal to head. 



