BY W. J. McKAY. 959 



wrong when he describes the whole tongue as composed of hyoglossi. 

 In Pseudechis the muscles arise from the anterior third of the hyoid 

 bones, while at the posterior third there is an interhyoid muscle; 

 the hyoid bones in this species being remarkable for their length. 

 The muscles are similar in Hydrosaurus to those described above. 



M. GENIO-HYO-GLOSSUS. 



M. maxillo-hyoideus^ Hoflfmann j Genio-hyoideuSy Meckel ; Vor- 

 wdrtszieher des Zu7igenheins^ D' Alton ; Genio-hyo-glossus, Owen 3 

 Genio-vagiens, Duvernoy, 



This muscle arises by two heads — the external from the junction 

 of the anterior with the middle third of the dentary, the internal 

 from the median raphe of the intermandibularis. The two heads 

 running backwards and inwards coalesce, and are inserted on 

 the lingual sheath, and on the anterior portion of the hypo- 

 branchial rods. 



These muscles are the main protruders of the tongue. The 

 corresponding muscles in Hydrosaurus resemble these very. closely. 



M. GENIO-TRACHEALIS. 



M. genio-frachealis, Owen, Duvernoy ; 3faxillo-laryngeus, 

 Hoffmann ; Vorwdrtszieher des Kehlkoirfes^ D' Alton. 



The genio-trachealis is a small band of muscles arising from the 

 same spot as the outer head of the genio-glossus. It runs back- 

 wards and inwards to be inserted on the side of the trachea ; at 

 the same time some fibres spread out on the lingual sheath and 

 the floor of the mouth. 



This muscle appears to represent a dismemberment of the 

 genio-glossus. The muscle is present in Hydrosaurus. The 

 action of the muscle is to protrude the trachea while the animal 

 is passing a large prey through its gape. 



M. HYO-TRACHEALIS. 



M. hyoideo-laryngeus, Hoffmann ; Rilckwdrtszieher des Kehlkopfes^ 

 D 'Alton ; Retr aliens laryngis, Hiibner. 



