636' GREAT BLACK-BACKED GULL. 



the rings 112, cartilaginous. The inferior larynx is greatly expanded 

 antero-posteriorly, and the first dimidiate ring is 5 twelfths in extent, 

 with a somewhat smaller ring beyond it. The lateral muscles are very 

 slender ; the sterno-tracheal, which passes off at the distance of ^ inch 

 from the bifurcation, is strong ; there is a slender slip on each side go- 

 ing to the bronchial membrane. The bronchi are wide, and formed of 

 20 half rings. 



The sternum is extremely singular, on account of its great width 

 and concavity, compared with its length; the latter being only 2^ 

 inches, while the breadth at the anterior costal processes is 2^ inches. 

 The crest is thus extremely short, but of considerable height, its most 

 prominent part being 10| twelfths. The coracoid bones are remark- 

 ably large, and so firmly fixed in the joint as to have just the slightest 

 perceptible motion. The furcula is also very large and wide, of the 

 form of the letter U, its crura at their union forming a large mass of 

 solid bone, continuous with the crest of the sternum. The posterior 

 edge of the sternum has a very slight sinus on each side. 



Now, in this bird, which is confessed to be inferior to none in its 

 power of flight, the sternal crest is not nearly so prominent as that of a 

 Grouse or Partridge, so that the supposed indication which this part af- 

 fords of vigorous flight is evidently fallacious. The sternum, although 

 much shorter, resembles that of the Pelicans, Cormorants, and Anhin- 

 gas, as well as in a less degree of the Gannets. 



GREAT BLACK-BACKED GULL. 



Larus marinus, Linn. 



PLATE CCXLI. Vol. in. p. 305. 



Male, from Dr T. M. Brewer. The mouth is of moderate width, 

 its breadth being 1 inch 9 twelfths ; the palate flat, with two very pro- 

 minent papillate ridges, and four series of intervening papillae ; on the 

 upper mandible beneath are five ridges, and the horny edges are promi- 

 nent and thin, but very strong ; the posterior aperture of the nares li- 

 near, 1 inch 9 twelfths long. The tongue is 2 inches 2 twelfths in length, 



