2 PROCEEDINGS OF THE NATIONAL MUSEUM vol.87 



diagnostic parts were present to indicate clearly that their affinities 

 are with this genus. They are the first recognizable remains of 

 Leptocemtops to be found in the Two Medicine formation, and their 

 discovery considerably extends the known geological and geograph- 

 ical range of this little-known dinosaur. A nearly complete artic- 

 ulated hind limb and foot contributes to a better understanding of 

 the skeletal anatomy, as a complete pes was previously unknown. 



The genus Leptoceratops was founded ^ upon an incomplete skeleton 

 from the Edmonton formation in southern Alberta, and in 1916 a fine 

 skeleton lacking the skull was discovered near the bottom of the 

 St. Mary River formation in Montana, which lies above the Two 

 Medicine. This latter specimen is now mounted in the American 

 Museum of Natural History. 



The occurrence of Leptoceratops in the Two Medicine formation 

 would suggest, on geological position alone, that it probably repre- 

 sents a species distinct from these found in the Edmonton and 

 St. Mary River formations. Comparison, however, fails to disclose 

 in the materials now available any character, except size, that would 

 serve to distinguish them. Through the courtesy of Dr. Barnum 

 Brown, limb and foot bones of Leptocemtops gracilis were lent me 

 for direct comparison, but the closest agreement was found in all the 

 bones contrasted. The much smaller size of the National Museum 

 specimens is in all probability due to immaturity, as indicated by the 

 open sutures of the skull parts and the noncoalescence of the vertebral 

 processes. For the present I shall, therefore, regard these specimens 

 specifically indeterminable in the hope that the discovery of more 

 complete materials will eventually clear up the uncertainty of their 

 specific identity. 



Specimen U.S.N.M. No. 13863 consists of the incomplete right 

 maxillary containing five worn teeth; a premaxillary portion con- 

 taining the roots of two teeth; six scattered teeth; distal half of right 

 femur; the tibia, fibula, tarsus, and nearly complete pes. All tliese 

 limb and foot bones were found articulated. Included also are shaft 

 portions of ih^ radius and ulna. Collected by George B. Pearce, 

 July 25, 1935, on the south side of Two Medicine River, Teton 

 County, Mont. 



Specimen U.S.N.M. No. 13864 was completely weathered out of the 

 ground, but from the fragmentary parts the following recognizable 

 elements have been pieced together: Nasals, supraoccipital, and por- 

 tion of parietal; frontals; numerous other unidentified skull parts; 

 four teeth; incomplete predentary; scapula; ischia; ilia; pubes all 

 incomplete; parts of ulnae, radii, femora, and tibiae, a few foot bones. 

 Dorsal, caudal, and sacral centra, pieces of ribs. Collected by George 



3 Brown, Barnum, Bull. Amer. Mus. Nat. Hist., vol. 33, pp. 567-580, 1914. 



