Cope.] "Ibtt f0ct< 20, 



molars arid part of the canine. The canine is small and the first premolar 

 in accordance with the generic character, is wanting. The second pre- 

 molar is two-rooted.. The fourth has an elevated principal cusp, and a 

 narrow heel on the inner side of the posterior base ; anterior base injured. 

 The first true molar has very little sectorial character, and resembles the 

 corresponding tooth of a Pelyeodus. It differs entirely from that of the 

 D. fimdaminis in the possession of a well marked posterior internal cusp, 

 which is connected by a ridge with the large internal lateral cusp of the 

 heel. The anterior cusps of opposite sides sub-equal. A weak external 

 basal cingulum on the anterior half of the crown ; no internal cingulum. 

 Enamel of the tooth wrinkled. 



Measurements. M. 



Length of premolar series 0140 



Elevation of P-m. iv 0040 



DiametersofM.il antero P ost « rior 0055 



i. transverse 0042 



Depth of Ramus at P-m. i 0090 



M 0113 



On comparison with the D. fundaminis, the first molar tooth has the 

 same dimensions, but the premolars are considerably smaller. The ramus 

 is also shallower. Found by Mr. Baldwin in the Puerco beds of North- 

 west New Mexico. 



Didymictis Jiaydenianus, sp. nov. 



This creodont is represented by parts of the maxillary and mandibular 

 bones of the left side, the former supporting the four, and the latter 

 supporting the three last molars. The arrangement of the superior molars 

 is much as in D. protenus, the fourth premolar being a true sectorial. The 

 third premolar has no internal lobe, although the section of the base of the 

 crown is narrowly triangular. It has anterior and posterior basal lobes, and 

 a posterior lobe on the cutting edge. In the sectorial the median lobe is 

 a good deal more produced than the posterior, though the two form together 

 the usual blade. The anterior basal lobe is distinct ; and the internal is larger 

 and is conic. The first true molar has the anterior external base of the crown 

 produced. Its two external cusps are conic and distinct. The internal part 

 of the crown is rounded and supports a conic internal tubercle, which is 

 separated from the external cones by two small concentric tubercles. The 

 second true molar is considerably, smaller, and is transverse, its external 

 border being very oblique. It has an acute internal lobe. 



The character of the species is well-marked in the inferior true molars. 

 The first has the form seen in other species of Didymictis. The heel is 

 large, and with a median basin between lateral cutting edges. The two 

 anterior inner cusps are of equal elevation and are near together ; the 

 external is much larger. The last molar is elongate, but reduced in size. 

 Its anterior three cusps, rudimental in other species, are here elevated, 

 forming the triangular mass seen in the first true molar. They are not so- 



