448 BULLETIN 54, UNITED STATES NATIONAL MUSEUM. 



slightly more than half as long as the upper margin, and the angle 

 between the lower margin and the palmar edge is less than 100; 

 the notch at the distal end of the lower margin is longer than in 

 S. occidentale. 



'"Abdominal shield is slightly longer than broad, otherwise as in 

 S. occidentale. 



" Uropoda seem to be only a little more than half as long as the 

 abdominal shield; the rami preserved only in the young female a 

 little shorter than in $. occidentale. 



"Length of the largest male 4.5 mm." HANSEN. 



Family XVII. JANIRID^E.* 



Lateral parts of head lamellarly expanded. Eyes, when present, 

 usually subdorsal. First pair of antenna? sometimes well developed 

 with multi-articulate flagellum, sometimes small with rudimentary 

 flagellum. Second antennae generally with small scale outside of third 

 joint of peduncle; peduncle composed of six articles. 



First pair of legs sometimes prehensile, sometimes not differing from 

 the six following pairs, which are ambulatory; dactylus generally bi- 

 or tri-unguiculate. 



First pair of pleopoda in female transformed into a single large oper- 

 cular plate, undivided; second pair wanting; outer Iamella3 of two 

 succeeding pairs, third and fourth pleopoda, narrow and confluent with 

 basal part; both branches well developed; fifth pair with only a single 

 branch. 



First pair of pleopoda in male coupled with the second pair and 

 forming a sort of compound operculum. The peduncles of the first 

 pleopoda are fused, are very long, with immovable single branches. 

 Second pair with the distal joint of the peduncle situated outside of and 

 coupled with the first pair of pleopods; the branches are attached to 

 the inner margin of the peduncle; the inner branch is geniculate, two- 

 jointed, the distal joint containing a cavity and being produced to a 

 point; the outer branch is very short, two-jointed, and hook-shaped. 

 The third, fourth, and fifth pairs of pleopoda are similar to those of 

 female. 



ANALYTICAL KEY TO THE GENERA OV THE FAMILY JAXIRID.E. 



a. Second pair of antennae long, well developed, with multi-articulate flagellum; 

 articles of peduncle not dilated. Mandibles with cutting part composed of one 

 or two serrated teeth. 



b. First pair of antennae extremely small, with rudimentary flagellum, composed 

 of only two articles. Second pair of antenme without a scale attached to the 

 peduncle. Uropoda extremely small, branches short, nodiform. 



Genus Jara Leach 



aProc. Zool. Soc. London, 1905, II, Pt. 2, pp. 326-327. 



'"'See Sars for characters of family, Crust, of Norway, II, 1899, p. 98, and Hansen, 

 Proc. Zool. Soc. London, 1905, II, Pt. 2, pp. 308-309, 315-316. 



