666 DR. p. CHALMERS MITCHiELL ON THE 



Muscular Anatomy. 

 Muscles of Head. 



Der'nio-temjiorcdis. — This thin but extensive sheet of muscle- 

 arose at each side by a fleshy, narrow head, behind and above the 

 temporal fossa and close to the origin of the biventer maxilla?, 

 and spread out on the skin of the ventral surface and sides of 

 the neck, precisely as in the Pelican. 



Biventer mccxillce was very large and strong, arising from a well- 

 marked area on the back of the head behind the quadrate and 

 inserted to the posterior end of the lower jaw. As in the 

 Pelican, I could not separate this from the underlying digastric 

 or depressor mandibula?. 



Temporal. — External portion. A very strong mass, arising 

 from the doi'sal part of the temporal fossa back to the biventei,. 

 runs downwards and forwards, dipping under the ramus of the 

 maxilla to be inserted to the outer and upper surface of the lower- 

 jaw opposite the orbit. 



Pyramidal portion. Strong fan-shaped muscle arising trans- 

 versely under the post-orbital process and converging to a rounded 

 tendon which runs forwards and outwards to the inner side of the 

 lower jaw. Parallel with this, and possibly a separate portion of 

 it, is a ilat band of muscle running from close to the articulation 

 of the quadrate, alongside the tendon of the pyramidal portion to 

 be inserted just anterior to it. 



Quadrato-mandibular portion. "Very strong fleshy muscle- 

 running transversely from the whole of the anterior surface and 

 forward process of the quadrate to the ramus. 



Quadrato-orbital portion. Long muscle from just behind the 

 optic foramen across to the whole inner edge of the orbital 

 process of the quadrate. 



Pterygoid. — An enormous mass of muscle, partly separable 

 into layers, on the lower surface of the jaw, from the posterior 

 angle and ventral posterior portion of the mandible lunning 

 forwards to the pterygoids. 



The temporal and pterygoid muscles are practically identical 

 with what I have found in the Pelican. 



Biventer cervicis. — I examined this muscle to see if tliere were 

 any trace of the peculiar formation described by Garrod in the 

 case of the Darters, but found that the mnscle with its anterior- 

 and posterior bellies was quite normal. 



Hyoid Muscles. 



Mylohyoid anterior. — As in the Pelican a very slender and thin 

 sheet of muscular fibres superficial to the other muscles of the 

 under surface of the jaws, and running transversely across fi'om 

 the ramus of the jaw to spread out on the interspace between the 

 two rami, but without meeting its fellow in a median raphfe. 



Mylohyoid jJosterior. — Arises as a broad strap from the outer 

 surface of the angle of the jaw just below the ear a,nd divides intO' 



