Vol. IX] VON G ELD ERN— FLORIDA CHAMELEON 323 



on the posterior horn, against the pull of the stemo-hyoid and 

 omo-hyoid. In this way the fulcrum is fixed. The muscles of 

 the tongue probably play a small part in the action. 



The retraction of the fan is accomplished by the elasticity 

 of the skin, the contraction of the fibres of the sterno-hyoid, 

 inserting on the processus retrobasalis and the pulling of the 

 anterior horns cephalad by the mylo-ceratoids. The elasticity 

 and spring of the entoglossus probably also aids to some 

 extent. 



For purposes of comparison, a dissection was made of the 

 hyoid apparatus of a large Iguana. (Figs, 5, 6, 7.) With the 

 exception of a well developed mylo-hyoid and for the reason 

 that none of the muscle fibres of the sterno-hyoid insert on 

 the processus retro-basalis, the structures were essentially the 

 same. 



VI 



Some difficulty was encountered in naming the muscles of 

 the hyoid apparatus. There was a question as to whether 

 the nomenclature of the earlier investigators should be re- 

 tained or whether these muscles should be given the names of 

 homologous structures in the mammalia. If the old names be 

 retained, which should be chosen among the various synonym- 

 ous terms ? If the muscles be named after mammalian homo- 

 logues another difficulty arises, for the names of muscles in 

 the mammalia usually represent the definite origin and inser- 

 tion and consequently the name may lose its significance and 

 become absurd when applied to a reptile in which there is a 

 different origin and insertion. It was finally decided to retain 

 for the most part the older nomenclature and leave the ques- 

 tion for further investigation. (See list of synonyms.) 



The same difficulty arose over naming the various struc- 

 tures of the hyoid apparatus. Again the older names were 

 retained with the exception of the processus retrobasalis. This 

 structure is called the posterior horn by Huxley, but since 

 this would necessitate the changing of the name of the true 

 posterior horn to middle horn, it was thought best to desig- 

 nate it by a new name. That it is part of the basi-hyal and 

 not a true horn is evident by following its embryological de- 

 velopment. 



