. Bulletin - United States National Museum. Science. 20 BULLETIN 110, UNITED STATES NATIONAL MUSEUM. immediately below the narial border is a deep longitudinal groove for the reception of a slender anterior process from the maxillary, otherwise the union of these two bones is by a straight vertical suture that is strengthened by a vertical median ridge on the posterior end of the premaxillary which fits into a corresponding de- pression on the anterior end of the maxillary. In Antrodemus the premaxillary carries five teeth, all of which, judging from the size of the aveoli and the two teeth pr
. Bulletin - United States National Museum. Science. 20 BULLETIN 110, UNITED STATES NATIONAL MUSEUM. immediately below the narial border is a deep longitudinal groove for the reception of a slender anterior process from the maxillary, otherwise the union of these two bones is by a straight vertical suture that is strengthened by a vertical median ridge on the posterior end of the premaxillary which fits into a corresponding de- pression on the anterior end of the maxillary. In Antrodemus the premaxillary carries five teeth, all of which, judging from the size of the aveoli and the two teeth preserved in this specimen, are of good size (fig. 10). The second aveolus contains a large worn tooth about to be shed and in the fourth aveolus is a germ tooth the point of which is just beginning to emerge below the dental parapet. Between the five aveolae are four well defined interdental rugosae. A careful comparison of this specimen with the right premaxillary figured by Marsh (on plate 12, fig. 1) Dino- saurs of North America (reproduced here as figure 11), as Creosaurus atrox fails to disclose any important differences, and since Lull has recently written me that this bone "mayor may not" belong to the type material, I am inclined to regard it as pertaining to the genus Antrode- mus, and probably also to the present species, though it pertains to a some- what smaller individual than the pre- maxillary described above. The pre- maxillary of Antrodemus is relatively longer than in Ceratosaurus, which carries only three teeth. It may be distinguished from Tyrannosaurus and Coelui'us iOrnitholestes) by the presence of four teeth in the premaxillaries of that genus. The greatest diameter anteroposteriorly of the premaxillary of No. 4734 is 105 mm.; its greatest depth from dental to nasal border is 83 mm. MaxiUary (m.).—The left maxillary of No. 4734 is almost entire and in a beau- tiful state of preservation. The functional teeth, with the exception of the ninth fr
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