178 Bulletin American Museum of Natural History. [Vol. XXVII, 



dence from other parts of the skeleton such resemblances in dentition can 

 not be trusted as sufficient evidence of close affinity (p. 108). 



Different members of the order inherit certain characters from very 

 remote possibly unknown prototherian or even Cynodont ancestors, as 

 follows : 



(1) The sharj) differentiation of premolars from molars (compare the 

 Cynodont Diademodon mastacus Broom, 1905.4, pi. x). Marsh gave the 

 character "premolars and molars imperfectly differentiated" as diagnostic 

 of the order Pantotheria but Osborn found (1888, p. 257, footnote) that 

 the premolars and molars were well differentiated in all the specimens 

 examined by him. 



(2) Pm4, a large pointed tooth projecting much above the level of nij. 

 This character seems to be quite typical. 



(3) Dental formula typically 1.^, C.j, P.^, M.gzg. This formula may 

 have given rise by reduction to those of both Marsupials and Placentals. 

 It was already approximated in Cynodont reptiles (r/. I.|, C.^, P + M? 

 in .^lurosuchv.^ (Broom, 1906.2, pi. x) and I.-, C.-, P.^, M.^ in Diademodon 

 (Broom, 1905.4, pi. X). 



(4) Canine often bifanged, more or less premolariform. 



(5) Incisors chiefly lateral in position, chin very long and slender, 

 opposite rami weakly attached at the symphysis. 



(6) Coronoid sometimes very broad, e. g., Amphitherium, but occa- 

 sionally narrower, e. g., Amhlotheriuvi. 



(7) Condyle, although often higher than in Triconodonts, still near 

 the level of the cheek teeth and looking more backward than upward. This 

 implies a descending glenoid region and together with the long mandible 

 also implies that the basifacial axis was not bent downward. 



(8) Corono condylar sinus not deep. 



(9) Angle often a small apophysis but more advanced than in Bia- 

 demodon. Angle sometimes ])artly inflected {Amphitherium prevosiii). 



(10) "Cerebral hemispheres smooth" Marsh. ^ Cerebrum probably 

 confined chiefly to the parietal segment; basioccipit.al segment probably 

 very short; rhinencej)halon probably large. 



(11) The foregoing characters taken in connection with the tuberculo- 

 sectorial lower molars, indicate a type of skull in the more generalized forms 

 {Amphitherium) which would resemble that of the smallest Didelphids 

 {Marmosa pusiUa, Pcramijs) in many characters. 



To these characters, inherited from very remote ancestors, it is probable 

 that we should add two others hitherto taken to be a sign of specialization, 

 namely : 



1 This chanu'ter is said to lie indicated in one of Marsh's specimens (Osborn, 18SS, p. 257). 



