110 STRUCTURE AND CLASSIFICATION OF JJIRDS 



The geniohyoid is in two distinct portions ; the posterior 

 division arises on each side from a ramus of the mandible ; 

 it passes backwards and is wrapped round the ceratohyoid 

 to its tip. The anterior portion also arises from the rami of 

 the jaw ; it is inserted upon the ceratohyal partly under and 

 partly distally to the insertion of the posterior division. 

 This muscle is sometimes a single muscle, as, for example, 

 in Palamedea. 



The genioglossus (entirely absent in Palamedea, &c.) is a 

 slight muscle, springs from the middle line near the chin, 

 and passes to the os entoglossum. 



The ceratoglossus is a strong muscle, arises from the outer 

 side of the ceratohyal ; it ends in a tendon which is inserted 

 along the side of the tongue almost to the tip. The muscle 

 in Palamedea, &c., is divided into two parts. 



The ceratohyoid arises from the inner side of the cerato- 

 hyal and is inserted on to the urohyal.- 



The sternohyoid (in Palamedea) is a band of muscle which ' 

 arises from the basihyal and entoglossus ; it spreads out 

 over the thyroid cartilage and trachea. 



The hypoglossals &Tce in PaZamecZea indistinguishable from 

 the ceratoglossus. 



Muscles of the Head 



The temporalis (in Palamedea) is divided into two 

 portions ; the superficial part arises from the whole temporal 

 fossa and from the external and internal surfaces of the 

 midtemporal process ; it runs to the outer upper surface of 

 the lower jaw ; the deeper part is a pyramidal muscle ending 

 in a stout tendon attached to the lower jaw ; in addition to 

 this another portion, deeper still, runs across from the forward 

 process of the quadrate to the inner side of the ramus, and 

 a wide band of muscle brid'ges the interval between the inner 

 edges of the forward process of the quadrate and the wall of 

 the orbit behind the optic foramen. 



The pterygoid is divided into several layers which con- 

 nect the lower jaw with the palatines and pterygoids. 



