Skull of Tritylodou longgevus, Owen. 287 



On the underside of tlie skull (text-fig. 3) the sutures 

 separating the premaxillaries from the niaxilhiries and the 

 paUitine processes oi" the latter are ahnost certain (com p. 

 Owen, 18b4, p. 147) ; but tlie suture between tiie palatines 

 and the maxiilaries is very doubtful. 



I have still to add that 1 can confirm the statement of Bronni 

 (comp. Broom, 1910^ p. 762) that there are in Tritijlodon not 

 two but three incisors. Indeed, in the front of the two 

 broken great incisors and near to the point where the two 

 premaxillaries are meeting one another there are two small 

 teeth-sockets (text-tig. 3). But Broom's statement {ib. 

 p. 762) that there are seven and not six molars in Trit>jlodon 

 I cannot accept, because the limit of the last molar on the 

 right side is a sharp one, and no plain trace of a molar behind 

 it is to be seen. I suppose, in consequence, the dental formula 

 of Trifylodon to be i 3, pm 1, m 5 *. 



According to my preceding statements, and to the previous 

 statements of Owen, Seeley, Osborn, and Broom, I add here, 

 in conclusion, a review of the mammalian and reptilian 

 characters of Tritijlodon. 



I. Mammalian Characters. 



1. Divided roots of molar teeth; 



2. Miiltituberculate teeth ; 



3. Straight and parallel rows of teeth; 



4. No postfrontal bone. 



From these four characters, the first is still the best proof 

 for the mammalian character of TriVj/Zot/o?2, no theromorphous 

 reptile, being known with divided teeth-roots. But, as some 

 doubts have been expressed about this division f, the prepara- 

 tion of the molar tooth in Triti/lodon by Owen has been some- 

 what enlarged, and the new preparation shows (comp. the 

 photograph in PI. X. fig. 2) that no doubt about that division 

 can be entertained, the bone between the two roots un- 

 doubtedly not being dentine (it has the same colour as the bone 

 in front of the forward root). As a new corroborative proof 



wrong. The posterior part of the skull would be in both cases almost 

 the same (comp. the restoration of it in text-fig. 1 with the restoration 

 of Broom in Broom, 1914, fig. 1, p. 119). 



* In 1914 Broom gives the dental formula of Tritylodon as being 

 probably i 3, c 0, j) 4, m 3 (comp. Broom, 1914, p. 120). 



t Comp. H. Gadow, 'Amphibia and Reptiles,' London, 1901, p. 309, 



