108 STKUOTUEE AKD CLASSIFICATION OF BIRDS 



Depressor Coccygis. — This springs from the transverse 

 proce'ss of the last sacral vertebra, and from the adjacent 

 surface of the ilio-sacral ligament. It is inserted on to the 

 transverse processes of the last three or four caudal vertebrae. 



Abdominal Muscles 



Obliquus Abdominis Externus. — The muscle arises from 

 the ribs and from their uncinate processes. It ends by an 

 aponeurosis upon the pubis. 



Obliquus Abdominis Internus. — Lies between the last 

 muscle and the next. It passes from the pubis, extending 

 on to ilium to the last true rib. A separate slip of this is 

 described as the quadratus lumborum, running from the last 

 false rib to the crest of the ilium. 



Transversus Abdominis. — This is the deepest of the ab- 

 dominal muscles. It springs from the pubis and preace- 

 tabular ilium, and its aponeurosis ends in that of its fellow 

 in the linea alba. 



Bectus Abdominis. — Springs from last sternal rib and 

 from sternum, and is attached to pubis. 



Transverso-analis. — This passes across the abdomen in 

 front of the cloacal aperture, and meets its fellow. It arises 

 either from the pelvis or from the transverse processes of 

 certain caudal vertebrae. 



Hyoidean Muscles 



Our knowledge of the muscles of the hyoidean apparatus 

 and the neighbourhood is chiefly due to Giebbl,' Gadow,'-' 

 and Mitchell.^ I mainly follow the latter in his account 

 of these muscles in Opisthocomus and in Palamedea. 



' ' Die Zunge der Vogel,' &c., Zeitschr. f. d. ges. KaUmoiss. xi. 1858, p. 19. 



' Beonn's Thierreich, ' Aves.' 



' 'A Contribution to the Anatomy of the Hoatzin {Opisthocomus cristatus),' 

 P. Z. S. 1816, p. 618 ; Beddabd and Mitchell, ' On the Anatomy of Palamedea 

 cornuta,' P. Z. S. 1894, p. 536. See also G. L. Dcvernoy, 'MImoire sur 

 quelques Partioularit^s des Organes de la Deglutition de la Olasse des Oiseaux,' 

 •Ac, Mim. Soc. Hist. Nat. Strasboiirg, ii. 1835 ; J. Kaozandee, ' Beitrage zur 

 Bntwioklungsgesohiohte der Kaumuskulatur,' Mth. Emir. Inst. Wien, 1883. 



