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Show 117' at present in my hands, but it is evidently nearer to the South American Toxvdon, Oweu, and Typotkerium, Gervais, than anything yet discovered in the North American Tertiaries. It is no doubt related to the Anchippodus, Leidy, and Tillotherium Marsh, ( which Marsh observes may be identical,) but difters from both in many points of the dentition. Char, specif.- All the incisors are regularly convex in front. The surface of attrition of the large ones trnncate, of the small ones oblique. The section of the large ones near the base is diamond- shaped, with one acute angle truncate and the other rounded. There are some shallow grooves on the sides, and on one side a more pronounced longitudinal shallow angulation. The enamel of these and of all the molars is smooth, and there are no cingnla on the latter. The transverse crests of the unworn true- molars support two tubercles, and the inner extremities of the crests of the premolars are produced in accordance with the oblique wearing of the incurved crown in mastication. Measurements. M. Length of incisor, largest, type 1 043 Width of incisor, largest, type 1 013 Depth of incisor, largest, type 1 018 Length of incisor, medium," type 1 034 Width of incisor, medium, type 1 006 Depth of iucisor, medium, type 1 014 Depth (?) of incisior, last, type 1 .009 Width of incisor, last, type 1 004 Length of incisor, type 2 031 Width of incisor, type 2 006 Diameterof crown of premolar { ^ n e ^ ; ; ; ; . " . . . i ; ; """["" Y^:":::: '. 010 Length of enamel of face externally 013 Length of enamel of face posteriorly 005 Length of crown of posterior upper molar 016 Width of crown of posterior upper molar 012 Length of crown of posterior lower molar 012 Width of crown of posterior lower molar 009 Size abont that of a fully- grown hog, ( Sus scYopha.) Portions of several individuals have been found. CALAMODON SIMPLEX, gen. et sp. nov. Char, gen.- Molar teeth subcylindric, prismatic, rootless; the crown only distinguished by its investiture of enamel, which exhibits a weak marginal inflection for a portion of the length. Enamel extending in a band on oue or both sides of the tooth to the base. Incisors rodent- like, carved, with a band of enamel on the anterior face, and obliquely- truncate extremity. A number of specimens, probably representing this genus, have been found, aud I select as typical those of an individual in which the molar aud incisor teeth occurred together. The form is evidently allied to Ectoganus, as the close resemblance of the incisor teeth demonstrates, but the molars are of a much more simple type thau anything yet discovered in this group, imitating superficially those of some Edentata. Char, specif.- Molar (? superior) longitudinally bent, the convex ( outer) face covered with enamel to the base. Euamel extending a much shorter distance on the inner face, and soon worn through by attrition on one of the other faces. Section of the base of crown a snbquadrate oval. A slight inflection of enamel on the inner and a still weaker one on the ( T) posterior border of the triturating face. Enamel with slight longitudinal ridges. Incisor much curved, strongly convex in transverse section, the enamel obscurely longitudinally ridged on both sides near the border. Section of one side slightly concave. These and other specimens indicate an animal at least as large as the American tapir. Measurements. M. Length of a molar 042 Diameterof the same 015 Diameterof incisor, transverse 019 CALAMODON ARCAMOSXUS, sp. nov. This Troxodontis represented by a portion of the skeleton of a specimen including several teeth, aud most probably by portions of another, which includes a large and perfect inferior incisior- tooth. The former displays the alveoli for molars and incisors, |