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Behind the Splenial lies a larger bone which has not, so far as 
I am aware, hitherto been detected in the Stegocephalian jaw. It 
forms nearly the whole lower half of the middle of the jaw. The 
sutures dividing it from the Dentary above, the Splenial in front and 
the Angular behind have all been clearly made out in many specimens 
of both Trimerorachis and Eryops. In Branson’s figure of the jaw 
of Eryops, it represents the anterior part of his Angular. There is a 
suture just in front of the foramen which he has failed to observe. 
In the anterior part of the inner side of the bone is an anterior 
foramen also leading into the cavity of the jaw. For this bone I 
propose the name Preangular. 
Behind the Preangular lies on the inner side of the jaw a large 
Prearticular, and on the outside a large typical Angular. The Angular 
is the very striking bone which forms most of the outer side of the 
Fig. 2. Inner side of Mandible of Dicynodon (Kannemeyeria) Sino cephalus. 
Much reduced. 
back half of Stegocephalian jaws. It forms large articulations with 
the Prearticular, and with the Surangular. It does not reach back 
to the posterior end of the jaw. 
The Surangular is a small bone in Trimerorachis which lies above 
the Angular and behind the Dentary. It forms the outer wall of 
most of the supra-meckelian fossa. Posteriorly the Surangular seems 
to be anchylosed to the Articular. In even perfectly preserved 
specimens I cannot find a suture. The limits of the bone are pro- 
bably as indicated in the figure. 
The Articular forms the whole of the broad articulation and the 
whole of the posterior end of the jaw. 
The Prearticular is large and extends well forward. All its 
borders can be readily made out. 
In front of the supra-meckelian fossa and forming its anterior 
and much of its outer border is the Coronoid. This bone has been 
