O. C. Marsh — Cretaceous Mammalia. 87 



the crown of the tooth especially fragile. The present type 

 specimen pertained to an animal somewhat smaller than a 

 rabbit. It is also from the Laramie deposits of Wyoming. 



Halodon scidptus, gen. et sp. nov. 



The present genus is an interesting form of the Plagiaulac- 

 idm, and the type specimen is represented on Plate III, 

 figures 11-13. It is the characteristic fourth premolar of the 

 lower jaw. It indicates an intermediate form between Ctenac- 

 odon and Plagiaulax. The summit of the crown is notched, 

 and there are seven distinct ridges on the sides. The posterior 

 third of the crown is smooth. 



An upper incisor, apparently the median one, was found 

 with the type specimen, and is provisionally referred to the 

 same species. It is represented on Plate III, figures 1-3. A 

 second incisor, much smaller, and apparently the exterior one, 

 is represented on the same plate, figures 7-10. 



A much smaller species, probably of the same genus, was 

 secured from the same horizon. The type specimen, a lower 

 third or fourth premolar, is represented on the same plate, 

 figures 14-17. The upper incisor shown in figures 4-6 of the 

 same plate is provisionally referred to this species, which may 

 be called Halodon serratus. 



The larger species was nearly the size of a squirrel, and the 

 smaller one, about as large as a rat. The remains representing 

 both are from the Laramie formation of Wyoming. 



Camptomus ampins, gen. et sp. nov. 



One of the largest mammals found in the Laramie is repre- 

 sented by the several parts of the skeleton, and fragments of 

 teeth, but the association of the various remains may be 

 accidental. The important character of the genus is seen in 

 the scapula, which has an articular face for a distinct coracoid. 

 This specimen is represented on Plate V, figures 1 and 2, and 

 may be considered the type. With it was found the inter- 

 clavicle, and also the calcaneum and astragalus, represented 

 on the same plate. 



It is probable that this genus should be placed in the order 

 AUotheHa, but future discoveries must settle this point. The 

 specimens now referred to this species are from the Laramie 

 of Wyoming. 



Dryolestes tenax, sp. nov. 



The only specimen so far found in the Laramie deposits that 

 resembles the Jurassic Pantoiheria is a lower jaw. In size and 



