13. XEMA. 



161 



Subfamily III. LARINiE. 



Key to the Genera. 



a. Tail considerably forked ; wings long ; hind 



toe very small, free 13. Xema, p. 161. 



b. Tail cimeate, the central pair of rectrices fully 



0'8 in. longer than the next pair and r9 in. [p. 167. 



longer than the outermost 14. Rhodostethia, 



c. Tail square, or very nearly so. 



a' . Hind toe moderately or well developed, 

 free ; lower third of tibia bare. 

 a". Bill always more than twice and 

 usually about three times as long as 

 it is deep ; nostrils linear or linear- 

 ovate 15. L.uiiJS, p. 169. 



h" . Bill very short, the length barely twice 

 its depth, stout, compressed ante- 

 riorly ; nostrils very small, ovate .... 16. Gabiants, p. 297. 

 b'. Hind toe joined to the inner toe by a rugose 

 membrane ; foot coarse, strong, the webs 

 considerably indented ; bill very short, [p. 299. 



obtuse 17. Leucoph^tjs, 



c'. Hind toe joined to the inner by a strong 

 serrated membrane ; all the nails large 

 and curved, webs and toes rugose ; tibia 



feathered nearly to the joint 18. PAGOPHiLA,p.301, 



d'. Hind toe obsolete or rudimentary ; tarsus 

 much shorter than the middle toe with 

 the claw ; tail with a slight tendency to 

 furcation 19. Rissa, p. 305. 



13. XEMA. ^_ 



Type. 



Xema, Leach in J. Ross's Voy. Baff. Bay, App. ii. p. Ivii, 



cum tab. (1819) X. sabinii. 



Creagrus, Bp. Naumamiia, 1854, p. 213 X. furcata, 



Chema, Beichenow, J. f. 0. 1889, p. 188 X. sahini. 



Range. Arctic regions, and down to 14° S. lat, on the American 

 side of the Pacific. 



Key to the Species. 



a. Smaller, wing 10'7a in.; bill rather short; entire 



head deep slate-grey, terminating in a dark black 



coUar sabinii, p. 162. 



b. Larger, wing 16 in. ; a white band at the base 



of the bUl; head sooty black, with no terminal 



collar furcata, p. 165. 



