trtli. 



LARID.E — THE GULLS AND TERNS - LARUS. 229 



Larus schistisagus. 



THE SLATT-BACKED 0T7LL. 



? Imths (T)ominicanus) fusccsccns, Biiucii, J. f. O. 1853, 100 (part). 



Larus cachin mm, KriTi,. Deiikw. L 1858, 330 (iico Pam-. 1826). — Stejn. Nntiircn, 1884, 6. 



Larus argeiitntus, var. cachinnans, Sciiuksck, Kcisc, Amiirl. I. 18tiO, 504. 



Liinis marinus, .Swixii. Ibis, 1874, 165 (iien Linn.). — Saunueks, 1'. Z. H. 1878, 180. — Ui.akist. 

 & riiVKii, Ibis, 1878, 217; Tiniis. Ass. Soc. .lap. VIIL 1880, 18!) ; ib. X. 1882, 104. — Si:i;ii. 

 Ibis, 187!>, 24. — Kiiiiiw. Bull. Nutt. Oiii. CIuli, 1882, 60. — Bkan, Pr. U. S. Nat. Mus. 1882, 

 168. —Nelson, Cmiso of tlu; Conviii, 1883, 107. — Bi.aki.st. Amend. List B. .lap. 1884, 20. 



Lnrus pchigkus, Taczas. Bull. Soe. Zool. Fi-niice, 1870, 263 (iicc liiii'cii) ; Orn. Faun. Vost. Sibir. 1877. 



? Jjurus a£inus, Xi;i,so.v, Cruise of the Corwin, 1883, 107 (Plover Bay). 



Larus schist isa{i us, Stk-ixeoek, The Auk, Vol. I. .July, 1884, 231. 



IIab. North Pacific, cliicfly on the A.iiatic :<iile. Japan (Bi.akiston & Pryer, Saunders, 

 ami .'^KEBOHM, 11. c.) ; Anioor River (Schrenxk) ; I'chring Island and Petropaulski, Kaintschatkii 

 (STi;,iNEfiEH) ; Plover Bay ? (Nelson) ; Unalashka (Bean) ; Herald Island, Arctic Ocean, and 

 I'lirt Clarence, Alaska (lliixiWAY, 1. c). 



Sr. Char. Adnlt $ (No. 9282.5, U. S. Nat. Mus., Behring Island, Kamtschatka, May 5, 1883 ) : 

 Head, neck, rump, upper tail-coverts, tail, and entire lower parts pure white ; mantle and wings 

 deep plumbeous, or bluish slate-gray, much darker than in L. nccidentaUs, and altogetiier more 

 bluish than in L. vutrinus. Four outer primaries slaty black, more grayish basally and on the 

 inner webs, the latter fading into bluish gray toward the edge ; outer quill with tlui terminal 2.10 

 ini'hes (measured along the shaft) white, both webs with a small blackish spot on the edge, about 

 .40 (if an inch from tlie tip ; second quill with the terminal white spot only .40 of an inch in 

 extent, but the inner web with a large oval spot of white, .90 of an inch long, and extending 

 entirely across, and situated .50 of an inch anterior to the termiinil white spot ; third quill with 

 the terminal white spot about the same size a.s that on the second, the inner web with a grayish 

 white space, beginning about 1.60 inches from the tip, abruptly defined, with a deeply convex out- 

 liui', against the black subterminal portion, but not distinctly contrasted with the plumbeous-gray of 

 tile remaining portion of the web ; fourth quill similar to the third, but the white spot rather more 

 distinct, and beginning only 1.30 inches from the tip ; fifth quill similar, but with the white spot 

 on the inner web still larger and still neai-er the tip (only I.OO inch), and the outer web dark 

 phuubeous-gray to within about 1.50 inches of the end, the extremity of this grayish portion obtusely 

 Wedge-shaped, and fading into white at the extremity ; sixth quill without any distinct black spot 

 on the inner web, which is white for .ibout 1.80 inches (measureil next the shaft) from the tip, the 

 white rather abruptlj' defined against the ]ilumbeous of the anterior portion ; outer web white for 

 .<)(> of an inch, then slaty black for about .70 of an inch (measured along the edge), the anterior 

 outline deeply concave, and enclosing a r.ather indistinct grayish while .space, which deepens gradu- 

 ally into the dark plumbeous-gray preceding it. Remaining primaries without any black, being 

 uniform deep plumbeous, with very broad and rather abrupt white tips. " Iris clear naples yellow, 

 or rather a yellowish cream-color ; bill deep ganiboge-yellow, with whitish tip an<l tomia ; an 

 orange-red spot on each side of the lower mandible ; angle of the mouth yellowish flesh-color ; 

 naked eye-ring reddish violet gray ; feet pinkish flesb-color, nails horny black, with whitish tips" 

 (Colors of freshly killed hii\\, fide Stejneher, MSS.). 



Wing, 18.10 inches; tail, 7.50; culmen, 2.35; depth of bill through base, .80, at angle, .90; 

 tarsus, 2.75 ; middle toe, 2.40. 



This species is apparently the North Pacific representative of Z. marinus, I'rom which it may 

 ea>ily be distinguished by the different color of the mantle, which is of a deep bluish slate, or 

 plumbeous, without any of the brown tinge that is always .seen in marinus. The lutter has no gray 

 "wedge" on the inner web of the first primary, and has on the second quill a subapical white 

 crossliar. The white subapical spot on the third primary of schistisagus is altogether wanting in 

 marinus. 



From L. cachiniuins the present bird diff'ers in having a very much darker mantle (cachmnans 

 being decidedly paler than occidentalis, while schistisagus is much darker), flesh-colored instead of 

 yellow feet, in being of larger size, and in possessing other marked characters. 



