100 ANNALS NEW YORK ACADEMY OF SCIENCES 



the birds and the reptiles are very close in their origin. The most im- 

 portant characters of the bird skull are : 



(1) Great expansion of the brain case with corresponding changes in 

 the base of the cranium. 



(2) Loss of the upper temporal arcade, the lower temporal arcade 

 (quadratojugal and jugal) being left intact. 



(3) Radical changes in the pterygoid and palatine region where great 

 changes occur even within the class. 



(4) Loss of teeth and assumption of a beak. 



(5) Loss of sutures and lightening of all the elements. The bird skull 

 is fundamentally similar to that of the primitive pseudosuchian Eupar- 

 Iceria capensis of Broom (1913). The maxillae, jugal and quadratojugal 

 articulate with the quadrate in true reptilian fashion, while the quadrate 

 is movable as in many reptiles. 



MUSCLES OF THE ADDUCTOR OR TEMPORAL GROUP 

 (INNERVATED BY V 3 ) 



Capiti-mandibularis. 



(a) Capiti-mandibularis superflcialis (C. m. s.). 



= Masseter of Shuf eldt and Gadow. 



(b) Capiti-mandibularis medius (C. m. m.). 



= Temporalis of Shufeldt, Gadow. 



(c) Capiti-mandibularis profundus (C. m. p.). 



Not present in Gallus. 

 Pterygoideus anterior (Pt. a.). 

 Pterygoideus posterior (Pt. p.). 



MUSCLES OF THE DEPRESSOR OR DIGASTRIC GROUP 

 (INNERVATED BY VII) 



Depressor mandibular. 



MUSCLES OF THE ADDUCTOR OR TEMPORAL GROUP 

 (INNERVATED BY F 3 ) 



The capiti-mandibularis mass of the bird is divided into separate 

 muscles, and we assume that they are represented in the reptiles as un- 

 separated parts of the capiti-mandibularis, and for that reason they are 

 given the names used in the reptiles. 



(a) Capiti-mandibularis superflcialis (C. m. s.). — This muscle may 

 be divided into two parts ; one rises as a tendon from the bony ridge of 

 the squamosal, above the auditory entrance; the other head which is 

 fleshy arises from the quadrate. The insertion on the mandible is by 



