. Carnegie Institution of Washington publication. 154 RÉVISION DES PELYCOSAURIA.. L'étrier : De chaque côté de l'basisphenoid est un os court, large, qui occupe la position d'un étrier. L'extrémité intérieure est plus petite, mais se termine en une surface plane ; juste en dessous de l'extrémité de l'os est percé d'un trou occipital. La bouche est bien conservé sur un côté. Il y a un grand vide médian- forme la partie postérieure des narines, mais il n'y a pas vacuities palatal. Les sutures entre les-pterj prevomers goids, palatines et ne peut pas être établie. Le prevomers sont fines plaques connexion antérieure et latera
2614 x 956 px | 22,1 x 8,1 cm | 8,7 x 3,2 inches | 300dpi
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. Carnegie Institution of Washington publication. 154 REVISION OF THE PELYCOSAURIA.. The stapes: On either side of the basisphenoid is a short, wide bone, which occupies the position of a stapes. The inner end is smaller, but terminates in a flat surface; just below the extremity the bone is pierced by a foramen. The palate is well preserved on one side. There is a great median vacuity form- ing the posterior nares, but there are no palatal vacuities. The sutures between the pterj-goids, palatines and prevomers can not be made out. The prevomers are thin plates connecting anteriorly and laterally with the premaxillaries and anter- iorly with each other; more pos- teriorly they are cut out on the median line, so that when the two were in position there was an elon- gate heart-shaped vacuity in the Fig. 70.—Diagram of the upper surface of the lower jaw of Edapho- median line. At the anterior end, saurm pogonias. where the two boues meet, there are four conical teeth on each bone; the posterior is the larger. The pterygoids articulate with the basisphenoid in the mid-line and send a strong process backward, which articulates with the inner side of the lower end of the quad- rate. There is no descending external process forming a buttress for the lower jaw, as in the other Pclycosaiiria. The line of union with the palatine can not be made out. Covering a large portion of the pterygoid and the palatine is an oval plate studded thickly with stumpy conical teeth irregular>' arranged. On the inner edge there are some teeth of smaller size. Most of the teeth are injured by decay, but it can be seen that the ends were very blunt, resembling the pharyngeal teeth of Labrus. The plate bearing the teeth is very heavy and extends backwards, underlying the anterior half of the temporal region. The hnver jaw of the left side is nearly perfectly pre- served. The sutures between the separate bones can not be made out. The anterior symphysis is very strong and was formed by the sp
