HEAD-MUSOLES IN GALLUS AND OTHER SAUROPSIDA. 545 



first branchial bar, whilst the sterno-hyoid extends from this 

 down the neck to the sternum (text-figs. 19, 26, 31, 34, 38, 

 pp. 525, 529, 534, 537, 543). 



This condition of the geuio-hyoid persists in the Chelonia, 

 Sphenodon, Lacertilia vera, Rhiptoglossa, and Ophidia. 

 In the Alligator the muscle, after passing through this 

 stage, becomes connected by tendon with the anterior end of 

 one of the muscles into which the sterno-hyoid divides. In 

 Gallus the primary stage — of insertion of the genio-hyoid 

 into the first branchial bar — is rapidly passed through, and 

 the hind end becomes inserted into the under surface of the 

 first basibranchial (text-fig. 17, p. 524) ; later on the whole 

 muscle atrophies and disappears. 



The sterno-hyoid divides in all Reptiles, except Ophidia, 

 into several parallel strips, some of which retain their original 

 attachment to the first branchial bar, whilst others become 

 inserted into the basihyobranchial. In the Alligator one of 

 the strips becomes connected with the genio-hyoid by tendon. 



In Birds the sterno-hyoid, which does not become divided 

 into parallel strips, gains a new insertion into the dorsal sur- 

 face of the first basibranchial (text-fig. 17, p. 524)); and 

 in most Birds, though not in Apteryx and some others, it 

 divides into anterior and posterior portions, e. g. in Gallus into 

 sterno-thyroid and thyreo-hyoid (text-fig. 17, p. 524). 



The lingual muscles of Reptiles are developed from the 

 genio-hyoid, and consist of a genio-glossus and hyo-glossus 

 (text-figs. 19, 20, 2G, 31, 38, pp. 525, 526, 529, 534, 543). 

 The former is attached in front to the anterior end of 

 Meckel's cartilage, and the latter behind to the posterior 

 branchial bar — just as is the muscle from which they 

 originate. 



The genio-glossus is attached posteriorly to the front 

 end of the basihyobranchial in the embryos of Chelone (text- 

 fig. 20, p. 526), Alligator, and Sphenodon; this condition 

 persists in the two former, but in Sphenodon the muscle 

 subsequently also spreads into the tongue. The muscle ends 

 free in the tongue in Agama, ChamEeleon, and Tropidonotus 



