104 U.S. NATIONAL MUSEUM BULLETIN 236 



Females Males 



Psamathe longicauda Philippi, 1840 P. longicauda Philippi, 1840 



{ = Scutellidium t(h)isboides Claus, 1866; P. sargassi G. O. Sars, 1916) 

 Canthocamptus? hippolytes Kr0yer, 1863 C. hippolytes Kr0yer, 1863 

 {= Machairopus minutus G. O. Sars, 1905; Machaeropus minutus Marine Biological 



Association, 1957) 

 Machairopus idy aides Brady, 1883 



Scutellidium arthuri Poppe, 1884 S. arthuri Poppe, 1884 



S. a. var. magnum Monk, 1941 



S. plumosum Brady, 1899a S. plumosum Brady, 1899a 



M. lenticularis Brady, 1910 



( = M. kerguelensis Brady, 1910, in explanation of figure) 

 P.fucicola T. Scott, 1912 

 M. australis T. Scott, 1912 M. australis T. Scott, 1912 



{ = M achairopus karletzi Pesta, 1928) 

 M. major T. Scott, 1912 

 Idya ligustica Brian, 1920 /. ligustica Brian, 1920 



( — P. machairopoides Monard, 1928) 

 S. antarcticum Lang, 1936c 

 S. purpurocincta Monk, 1941 



S. lamellipes Monk, 1941 S. lamellipes Monk, 1941 



M. intermedins Nicholls, 1941 M. intermedins NichoUs, 1941 



M. cockburni Fairbridge, 1944 

 S. loureiroi Jakobi, 1954 



The position of the following species is uncertain : 



M. digitatus Brady, 1910 M. digitatus Brady, 1910 



M. sarsi Brady, 1910 



Machairopus sanctacrucis I. C. Thompson, 1888 (probably a calanoid copepod) 



A new species will be described below as : 



Scutellidium dentipes, new species 



Of the species listed above some are insufficiently known and may 

 on closer examination, turn out to be identical with older forms. 

 Scutellidium arthuri, S. arthuri var. magnum, S. purpurocincta and the 

 new species ;S'. dentipes form a complex which, after the study of more 

 material, may well appear to represent one somewhat variable species. 

 S. cockburni is very closely allied to S. australe, and S. loureiroi differs 

 from S. longicauda in minor particulars only. The following keys 

 may serve to distinguish the females and males. 



Key to the Species of Scutellidium 



FEMALES 



1. Furca as long as wide or wider than long 4 



Furca longer than wide 2 



2. Exopodite of leg 5 long, 4 times as long as wide . . S. lenticulare (Brady) 

 Exopodite of leg 5 shorter, 3 times as long as wide 3 



3. Exopodite of leg 5 with 4 apical setae, in addition to a seta at the external 



margin and some transverse rows of spinules . . S. antarcticum (Lang) 



