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sent paper it will be unnecessary to do more than figure the jaw in 
Trimerorachis, which is the smaller and more primitive genus. 
As seen in Fig. 1, A, the Dentary is a long bone extending 
nearly the whole length of the jaw but presenting no remarkable or 
unusual features. Below it are three elements which will require 
further discussion. Of these elements the most anterior is that which 
I have called Splenial. 
The term Splenial has been used for different bones, but Warson 
has clearly shown by tracing down from the higher reptiles that the 
Fig. 1. Mandible of Trimerorachus insiquis Corr, about 3/; nat. size. A. Outer 
side; B. Inner side; C. Under side. 
Splenial is the bone which les along the anterior part of the lower 
border of the jaw, and usually enters into the symphysis. This is 
the bone which Branson has figured in Eryops and Anaschisma, but 
has left unnamed. Warson has identified it in Loxomma, Micro- 
pholis, and Bothriceps. In Eryops and Trimerorachis it can be readily 
made out. Its position and relations in the latter will be readily seen 
in the figures. It lies mostly on the inner and lower sides, but also 
appears on the outer side of the jaw. 
