14 Annals of the Ornegie Museum. 



(No. IOI2, Carn. Mus. Cat. Vert. Fos.), and two quadritubercular 

 (No. 1685). They may all belong to one individual as they were 

 found near together. The two quadritubercular teeth are apparently 

 the corresponding premolars of opposite sides. Whether they are the 

 third or fourth of the series is difficult to determine. Their antero- 

 posterior diameter is nearly equal to that of the second premolar. Ac- 

 cording to Cope's figure^ of Chirox plicatiis, F^ and F^ are nearly 

 equal in length while F^ is smaller. These teeth apparently represent 

 a much smaller animal than the one described by Cope. 



mm. 



Antero-posterior diameter of P^ (No. 1012) 3. 



Transverse diameter of P^ (No. 1012) 2.6 



Antero-posterior diameter of /'2. (?) (No. 1685.-^) 3.3 



Transverse diameter of /'i (?) (No. 1685//) 3. 1 



From beds of rather soft greenish sandstone (Silberling quarry) 

 near Bear Butte, in the northern portion of Sweetgrass County in 

 Montana. Collected by A. C. Silberling. 



No. iioi consists of four teeth, two at least of which belong to the 



genus Chirox. They are quadritubercular and are somewhat smaller 



than those just described. They are probably fourth premolars. A 



triangular pyramidal tooth may be a F^ or ante-premolar of Chirox. 



Collected by Silberling in 1903 from the Silberling quarry east of 



Bear Butte. 



Family PLAGIAULACID.E Gill. 



Ptilodus Cope. 



(Am. Nat., XV, 1881, p. 921.) 

 In the collection there are quite a number of teeth oi Ftilodus con- 

 sisting of molars, premolars, and incisors. Probably two or three 

 species are represented. The teeth are associated with remains of 

 reptiles, and with eutherian mammals (^Pantolambda, etc.). 



Ptilodus montanus sp. nov. 



(Type No. 1673, Carnegie Museum Catalogue of Vertebrate 

 Fossils.) 



The type consists of a last lower premolar and a first lower molar 

 inserted in a portion of the left ramus of a mandible. 



Crown of F^ semi-eliipiical in a lateral vietv ; crown not high, and 

 upper portion of cutting-edge not extretnely convex ; eleven distinct and 

 two posterior indistinct ridges on the crorun ; Afj nearly one half the 



"^American Naturalist, Vol. XXI, June, 1887, p. 566. 



