T^XIDDONTA. 189 



sors rodent-like, ver}' large; third incisors large, with conic roots, faced with 

 enamel in front only. Canines placed obliquely to the long axis of the 

 ramus, their long horizontal axis extending inwards and backwards. Enamel 

 confined to their narrow anterior and posterior faces. Molars subcylindric 

 and with conic roots, one or more of them within the base of the coronoid 

 jjrocess. Form of the jaws deep and robust. 



A characteristic feature of the dentition in this genus is the thick coat- 

 ing of cementum, which invests those portions of the molars and inferior 

 canines which are not protected by enamel. In these teeth it is thicker 

 than the enamel, and forms thickened raised borders surrounding the latter, 

 producing a characteristic appearance not known in the other genera." It 

 is not observable in the large inferior incisors. 



A part of the skeleton of one of the species is preserved. It shows 

 that the humerus was robust, and was pierced distallj^ by a large arterial 

 foramen The condyles are not very convex, nor the internal epicondyle, 

 so prominent as in some of the Creodonta. The head of the radius is flat 

 and incapable of rotation, and the shaft is rather slender, while the ulna is 

 deep and thin. An ungual phalange is stout and compressed, and but little 

 curved, and without the basal sheath seen in some Carnivora and Edentata. 



The exact homologies of the seven mandibular teeth are obscure, and 

 it is uncertain to how many the expression molar should apply, since the 

 wear of all in my specimens is nearly equal 



The synq)hysis is solid and long; it projects wedge-like between the 

 large incisors, whose anterior borders are closely approximated. Tliere is 

 a largo mental foramen. 



Two species, the C. arcamcenus and C. simplex, were found by myself in 



New ]\Iexico. A third one, discovered by Mr. J. L. Wortman in the Wind 



River beds, has been described by myself under the name of C. cijlindrifer; 



it is not sufficiently well preserved to settle finally the question of its generic 



position. 



Calamodon simplex Cope. 



Report Vert. Foss. New Mexico, U. S. Geog. Surv. W. of lOOtb Meridian, C.apt. G. M. Wlieeler, 1874, p. 

 5. Repi rt U. S. Geog. Siirvs. W. of lOOtb Mcridi.iu, Capt. G. M. Wheeler, 1874, iv, ii, p. 166. 

 PI. xlii, figs. (V-S; xliii; xliv, figs. 2-5. Pal. BiiUetiu No. 34, p. 147, 1882. 



Plate XXIV c. Fig. I. 



The nearly complete mandible of this species was obtained by J. L. 



