ADAMS, PHYLOGENY OF THE JAW MUSCLES 99 



(a) Capiti-mandibularis superficialis (C. m. s.) = Masseter portion. 

 Arises on the quadratojugal, squamosal and quadrate. 



(b) Capiti-mandibularis medius (C. m. m.) — This is the inner part 

 of the temporal sheet arising on postfrontal, prootic, squamosal and quad- 

 rate under the fibers of the outer or masseteric portion. These two slips 

 are not separate. 



(c) Capiti-mandibularis profundus (C. m. p.). — The deeper portion 

 of the mass. It arises on the parietal and is inserted on the coronoid 

 along with the rest of the capiti-mandibularis. (A lower part of this 

 muscle arises from the columella cranii and is considered as pterygoideus 

 posterior.) 



Pterygoideus anterior (Pt. a.). — This muscle arises on the whole outer 

 surface of the pterygoid (except the branch to the palatine) and is in- 

 serted on the posterior part of the jaw. 



Pterygoideus posterior (Pt. p.). — This with the exception of the lowest 

 part arises on the columella cranii and is inserted on the mandible, 

 posterior to the insertion of the capiti-mandibularis profundus. 



Pterygo-parietalis (Pt. par.). — This muscle is peculiar to reptiles with 

 a rodlike columella cranii. It arises on the downward projection of the 

 parietal and is inserted on the whole upper surface of the pterygoid, im- 

 mediately in front of the articulation with the columella. It seems to 

 represent a part of the inner layer of capiti-mandibularis profundus that 

 separated off for the service of the pterygoid. The same might be said 

 of the muscle following. 



Pteryqo-splienoidalis posterior. — This muscle arises on the basisphe- 

 noid below the gasserian notch and is inserted on the upper and lower 

 surface of the pterygoid for its whole length to a level of the articulation 

 of the basipterygoid process of the sphenoid and the pterygoid. It pulls 

 the pterygoid upward and backward. This may represent a lower slip 

 from the capiti-mandibularis profundus. 



MUSCLES OF THE DEPRESSOR OR DIGASTRIC GROUP 

 (INNERVATED BY VII) 



Depressor mandibular (D. m.). — It arises on the parietal and nuchal 

 fascia and is inserted in the end of the mandible. 



Aves 



GALLUS 

 Plate VIII, Figs. 1, 2, 3 



The musculature of the bird, Gallus, follows in most particulars that 

 of reptiles. It offers one of the most convincing items of evidence that 



