228 STRUCTURE AND CLASSIFICATION OF BIRDS 



to MAcGiLLiYEAT ! ) has as many as thirty-four rings, which 

 are complete and not semi-rings. There seem to be two 

 pairs of extrinsic muscles, which form a very prominent 

 muscular mass, as in Passeres. Dr. SHUFELDT was unable 

 to find any sterno-trachealis. 



The tongue in the swifts is short and sagittate, with 

 a spiny base. It is constantly bifid at the tip. 



In the humming birds, as is well known, the long tongue is 

 tubular, and for its support the hyoids are bent over the top of 

 the, skull, as in the woodpeckers. The tongue itself ' is double 

 right down to the unpaired part of the os entoglossum, 

 whilst each of the two distal prolongations of the entoglossal 

 bone or cartilage is surrounded by a horny sheath, which is 

 curled upwards and inwards, in a similar fashion to what 

 we have seen in the Nectariniidae. In many species the 

 outer and inner edges of these tubes, however, are entire 

 and not laciniated. Thus the Trochilidae have developed 

 the highest form of tubular tongue ' (GrADOW 2 ) . 



The gizzard of the humming birds is remarkably small ; 

 that of the cypselids presents no remarkable characters, 

 and SHUFELDT has remarked upon the large size of the 

 liver in the humming birds as compared with the swifts ; 

 in both the right lobe is larger than the left, and there is a 

 'gall bladder in the swifts. 



Caeca are entirely absent in the Macrochires. 3 The 

 following are intestinal measurements of the swifts :- 



Cypselus apus ..... 6-25 inches. 

 Dendroclielidon coronata . . . 4'30 ,, 

 Cluftura caudacuta . . . .10 ,, 

 Cypselus alpiniis . . . .10 ,, 



Vait.i-i ..... 3'25 ,, 



A careful account of the trochiline and cypseline skeleton 

 will be found in a memoir by SHUFELDT. 4 Though this 



1 In AUDUBON'S Birds of N. America. 



- ' On the Suctorial Apparatus of the Tenuirostres,' P. Z. S. 1883. 

 :i CRISP, ' On some Points relating to the Anatomy of the Humming Bird 

 (Trochihts colubris),' P. Z. S. 1862, p. 208, observed a ' rudimentary appendix.' 

 1 ' Contribution to the Comparative Osteology of the Trochilida?, Caprimul- 



