Vol. IX] VON G ELD ERN— FLORIDA CHAMELEON 325 



VII 



I was unable to find any literature on the hyoid apparatus 

 of Anolis, but Dr. A. Chemin gives a good description of the 

 hyoid apparatus and its relation to the throat-fan in Colotes 

 versicolor. From the drawings in his paper there is a simi- 

 larity between the hyoid apparatus of Colotes and Anolis, but 

 the action varies markedly. Chemin considers the hyoid ap- 

 paratus as a lever of which the basi-hyal forms the fulcrum, 

 the processus entoglossus the power arm, and the processus 

 retrobasalis the weight arm. He believes that the processus 

 retrobasalis is made to swing cephalad and ventrad by press- 

 ure exerted in the dorsal direction on the processus ento- 

 glossus. This pressure is brought about by the pulling of the 

 basi-hyal ventrad by means of the sterno-hyoids and since the 

 processus entoglossus is prevented from moving ventrad with 

 the basi-hyal because of a band of tissue extending from one 

 hyoglossus to the other, the basi-hyal would rotate as the ful- 

 crum and swing the processus retrobasalis forward. The 

 cerato-hyoids simply pull on the anterior horns and increase 

 the angle between the first and second parts. Chemin states 

 that preceding the distension of the fan the animal swallows 

 air and distends its dilatable pharynx. 



Evidently then, according to Chemin, the greater the dis- 

 tension of the fan the greater must be the ventral excursion 

 of the basi-hyal, since that is the only way in which pressure 

 can be brought to bear on the processus entoglossus or the 

 power arm of the lever. The anterior and posterior horns 

 merely act as braces. 



It is also evident that in Colotes the most important muscles 

 are the sterno-hyoids, since these pull the basi-hyal ventrad. 

 The cerato-hyoid plays a minor and insignificant part. 



I have no desire to contradict the conclusions of Chemin 

 on the mechanism of the production of the throat-fan in 

 Colotes, but I cannot agree with the general statement that 

 the mechanism in Colotes is essentially the same for all the 

 Iguanidse. Certainly it differs markedly in Anolis where the 

 processus entoglossus is not the arm of the lever and only 

 acts as a hindrance to the production of the throat-fan. In 

 Anolis the cerato-hyoids play the most important role and the 

 sterno-hyoids a minor role. Furthermore, the production of 



