\:>,\ ANAA/jS NJ'JW YOIIK ACA/HLMV of HCIENOEfi 



muhvlFjH ()/'' TiiH i>i:i'i!i:ssni! on dkiahthk; ditoui' 



(INNIUtVATI'H) liY VII) 



^riiis Jiiiisclc is constant in tiio Rofitilia nnd its JnHoriion is evident on 

 the speoimen No. 5027, American Museum. \n many reptiles where the 

 l)jick p;ifl, of t,li(! skull Ik not ^rrcalJy inodificd its ori;rin is on the parietal, 

 hill, lii'i-(! it, seems to have been on tlie jtaroeeipital. '^I'he muscle arose on 

 the vctitral ejid of the par(;ccipilals, the ventral ends of which are roug?i- 

 ciicd for a niiisch; ijisertion. Its insertion on the mandible was on the 

 ;ii'l.icid;n', post(;rior to the iirt icniiit iii^'' sufface, wlierc there is a depression 

 simibir to tliat seen in most re[)tiles. 



Cynognatikjs 



Plato XIII, Figs. 2-.'5 



The skull is reptilian as a whole, hut parts of it very plainly show the 

 mammalian characters, especially the squamosal, the Jugal, the dentition 

 and the basicranial region. The quadrate is reduced. The jaw, although 

 Hiptilian, is of a type that foreshadows that of mammals. The dentary 

 h;ul cnhiriicd from the primitively slender dentary of the early reptiles 

 until if, was the most important part of the mandible and muot have car- 

 ried the greater part of the musculature. The coronoid process of the 

 dentary is large and ascends far into the temporal fossa. The angle of 

 the dentary is developing and shows plainly. The posterior part of the 

 jaw, consisting of the articular and other elements, is becoming small 

 and is so loosely attached to the dentary that in fossil specimens it is 

 usuiilly missing or found separate from the skull. The old reptilian 

 articulation with the skull had become reduced, but was still functional. 

 Alihougli the new articulation with the jaw had not yet been formed, I 

 infer, from the shape of the temporal fossa and from the direction of the 

 muscles, that the jaw was pulled not directly against the quadrate but 

 toward a point above it on the squamosal. 



MUSCLES OF THE AnDUCTOR OR TEMPORAL GROUP 

 (INNERVATED BY V^) 



Capiti-mandibularis. 



(a) Capiti-man(hbularis superficialis. 



(h) Capiti-mandibularis medius. 



(c) Capiti-mandibularis profundus. 

 Pterygoideus anterior. 



