222 STRUCTURE AND CLASSIFICATION OF BIRDS 



intrinsic muscle of the syrinx in this, as in the other smaller 

 hornbills, is very much larger relatively than in the larger 

 species. 



Anthraceros malayanus, again, is a little different from 

 all the types hitherto described. The last tracheal rings are 

 but little fused posteriorly ; only the penultimate and ante- 

 penultimate rings are so fused, so that it is impossible to be 

 certain as to the origin of the pessulus. The intrinsic muscles 

 are slender. 



Toccus presents certain peculiarities which I have not 

 yet observed in any other hornbills ; the trachea has two 

 pairs of extrinsic muscles, given off about half an inch apart. 

 This condition seems to me to be so remarkable that I have 

 preserved the specimen which shows it, though unfortunately 

 the insertions of the anterior pair of muscles are lost, and I 

 have no recollection of where the point of insertion was. 

 The intrinsic muscles 'are relatively small. There appears 

 to be no fusion between any of the tracheal rings. 



Cryptornis of the upper Eocene of France is held by 

 Milnb-Bdwaeds to be a hornbill. 



The family TJpupidse ' contains only the well-known 

 hoopoe (Upupa) and the but 'little known Irrisor and 

 B hinop omastus. 



There is a large feathered oil gland, but the after shaft is 

 absent or rudimentary. There are ten rectrices. 



The feather tracts are narrow. The ventral tract divides 

 very early on the neck, and gives off on each side in the 

 pectoral region an outer branch. At the base of the neck a 

 triserial tract is given off to the humeral tract, and just 

 below it a uniserial tract to the patagium. Between the 

 outer and inner branches of the ventral tract is a single row 

 of feathers. 



The dorsal tract encloses a spindle-shaped space, the 

 pterylse enclosing which are somewhat dilated in the ruiddle. 



' Stmokland, ' On the Structure and Affinities of Upupa and Irrisor,' Ann. 

 Mag. Nat. Hist. xii. (1843), p. 238 ; Mubie, ' On the Upupids and their Bela- 

 tionships,' Ihis, (3) iii. 1873, p. 181. 



