| * 
' 
30 Fretp CoLumbpian MuseuM—GEeEo tocy, VoL. II. 
anterior prolongation the angular, as does Baur. From the fact 
that the bone on the inner side of the dentary, covering Meckel’s 
groove, is the only one which can with propriety be called ‘‘splenial”’ 
(a ‘‘ bandage” or ‘‘patch’’), or opercular (a cover), it will be better to 
retain the former name for the element, as usually applied, and to 
give anew name to the part separated from the articular, wherever 
it exists as an independent bone; it may be called the prearticular. 

Fig. 4. 
Right mandible of Clidastes tortor Cope. D., dentary; sf., splenial; fra., prearticular; azg., 
angular; cov.,coronary; art., articular; sar, surangular. 
I assume that the element containing the cotylus must be the 
articular, and that the one in front of it, back of the coronoid and 
dentary, must be the surangular, though, as already stated, I can find 
no positive evidence of a separating suture in the present specimen, 
as 1s also the case in the adult SAkenodon mandible. Doubtless in 
some more fortunately*preserved specimen, or in one of a younger 
animal, the separating suture will be traced. I will add that the 
suture indicated by Cope* in his figure of the skull of Cemo/asaurus 
snowll, as separating the articular from the surangular, does not exist 
in the specimen; the place is indicated by a mere groove only. 
The angular is very long, and is extensively visible from both 
within and without. On the outer side it is seen reaching to a little 
beyond the proximal end of the symphysis, where the pointed extrem- 
ity is visibly intercalated between the dentary and a small portion of ° 
the splenial. On the inner side, the suture follows inward below the 
cotylus to the anterior inner angle of the articulation, near which it 
passes upward to meet the prearticular. The bone passes beneath 
this latter element but its connection with the surangular cannot be 
made out. Along the inferior border of Meckel’s groove and the 
splenial, the suture goes forward to near the proximal end of the 
symphysis. ‘ 
On the inner side of the mandible, there is an extraordinary 
arrangement of the bones. After much deliberation, I interpret them 
* Proc. Amer. Phil: Soc: 1894; 
