4 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxiv. 



If we want to include Callomysis as well as the Amblyops and 

 Erythrops groups into this subfamily, we are to alter slightly the 

 above diagnosis of the Leptomysinse as given by Norman, and put 

 it the following way: 



Subfamily : Leptomysinse. 



Outer uropods one- jointed, their outer margin setose. Gnathopods 

 (second cormopods) conforming in general character of the endopo- 

 dite to the maxillipeds (first cormopods). First true legs (third 

 cormopods) similar to the following in general character, and not 

 very greatly developed and longer than the latter. Male toith all the 

 pleopods well developed, and adapted for sioimming ; second to fifth 

 pair biramose, and never resembling those of the female. Sometimes 

 one of the branches of the fourth (rarely the third) pair ?nodified 

 for sexual purposes, in being slightly lengthened and possessing pe- 

 culiar setce on the terminal joints. 



The folloAving key of the genera of Leptomysinse mentioned above 

 may be convenient for their identification. No complete revision of 

 the subfamily is intended. 



KEY TO GENERA. 



a 1 . Eyes rudimentary, lamelliform. Male pleopods very uniform, the first with 

 inner branch rudimentary, the second to fifth with two subequal branches. 



Amblyops Sars and Pseudónima Sars. 

 a 2 . Eyes not lamelliform, more or less globular. 



u 1 . Telson short, sometimes hardly longer than wide, always much less than 

 twice as long as wide. Outer margin not spinous (or rarely so, in 

 Euchwtomera) . Apex not cleft. Male pleopods very uniform, the second 

 to fifth with two subequal branches. 



Erythrops Sars, a Parerythrops Sars, & Euchwtomera Sars. c 



if. Telson longer, generally at least twice as long as wide. Outer margin 



always spinous. Apex entire or cleft. Male pleopods less uniform ; 



one branch of third or fourth pair generally longer than the other (the 



prolongation sometimes only caused by the presence of a terminal spine). 



&. Pleopods of female rudimentary, simple. Outer or inner branch of 



fourth pleopods of male with tendency to become lengthened. 



d\ Outer margin of antennal scale setose, without distal spine. Outer 

 branch of fourth pleopods of male with tendency to become length- 

 ened, its terminal joints only slowly increasing in length, if at all. 

 e\ Telson elongated, linguiform, apex pointed or rounded, not cleft. 

 Three last joints of outer branch of fourth pleopods of male with- 

 out setae,, but with three strong spines. Antennal scale very long, 

 narrow, pointed Lcptomysis .Sars.^ 



a Sars, Monogr. Mysid., I, 1870, p. 11; Norman, in Ann. Nat. Hist. (6), X, 

 1S92, p. 159. 



h Sars, Idem, p. 40. 



c Sars, Kep. Voy. Challenger, XIII, 1885, p. 211. 



ô Sars, Monogr. Mysid., HI, 1879, p. 29; Norman, Ann. Nat. Hist. (G), X, 

 1892, p. 242. 



