44 Annals of the Carnegie Museum. 



Anteio-posterior diameter of P 2 5 



Antero-posterior diameter of P ¥ 5 



Anteroposterior diameter of P^ 9 



Transverse diameter of P4 4 



Antero-posterior diameter of M T 14 



Transverse diameter of M T , posteriorly 7 



Antero-posterior diameter of M- 2 •.... 22 



Transverse diameter of M^ 7 



Antero-posterior diameter of M3 32 



Transverse diameter of M-3, anteriorly 6 



In 1900 Mr. J. B. Hatcher discovered in the Harrison beds, por- 

 tions of both mandibular rami (No. 1241) belonging to an adult 

 animal. These are here referred to Stenomylus gracilis. 



Fig. 9. External view of right mandible of Stenomylus gracilis. \ nat. size. 

 No. 1 24 1. 



Brachypsalis simplicidens sp. nov. 

 (Type. No. 1553, Carnegie Museum Catalogue of Vertebrate Fossils.) 



The right mandibular ramus (No. 1553) on which this species is 

 established has the entire dentition, except the incisors, in place. The 

 posterior portion of the angle is not preserved. The specimen was 

 found in the Harrrison beds, on Agate Spring Stock Farm, Sioux 

 County, Nebraska, by Mr. Harold J. Cook, who presented it to the 

 writer. 



In comparing this specimen with Potamotherium lacota Matthew & 

 Gidley, and also with the type of Brachypsalis pachygnathns Cope, cer- 

 tain resemblances are found, more especially in the latter species. The 

 deep, short, and robust jaw with large teeth is especially characteristic 

 of the two forms. 



