448 MEMOIRS OF THE CARNEGIE MUSEUM. 



outward extending process seen in R. bicornis. Nor is the proximal end so much 

 expanded laterally as in the African species. 



The tibial border of the rotular trochlea is greatly developed; it has very nearly 

 reached the extreme modernized stage of development seen in the recent Rhinoceros 

 and the horse. The antero-posterior diameter of the distal end is therefore greater 

 than the transverse in approximately the same proportion as in R. bicornis. 



The patella is triangular in general outline, due to the large development of 

 the internal process in order to cover the greatly developed internal border of the 

 rotular trochlea described above. The trochlear grooves of the patella are quite 

 uneven in size and the bone as a whole unlike that of the horse. 



In fully adult and old individuals both ends of the tibia and fibula have a 

 strong tendency to become coossificd. This is a direct indication of the progressive 

 development which has reached its culmination in the completely united tibia and 

 fibula of R. bicornis. Like the femur, the tibia and fibula are rather long and slender, 

 when compared with these bones in the recent species, and it also appears that 



Fig. 37. Diccrathcrium cooki Peterson. No. 1840, Coll. Carnegie Musonm. Posterior and anterior 



views of patella. X i. 



these bones in Coenopus tridactylus (Osborn) are proportionally shorter and pos- 

 sibly also somewhat heavier than in D. cooki. 



Pes. Pis. LXIII, LXIV. As is already known, the pes is strictly tridactyl. 

 It is on the whole narrow and quite high, especially when compared with R. bicornis. 

 It is also somewhat higher and slenderer than the pes in Coenopus tridactylus. 



The tuber of the calcaneum has about the same general proportions as the 

 European species D. (?) croizeti Pomel*, i.e., it is quite heavy and of medium length, 

 while the sustentacular facets are similar in detail. The broad and rather low 

 astragalus also agrees in detail with that of this European form. The cuboid is 

 quite high and has an extremely heavy process posteriorly. The metatarsals are 

 quite elongated, the lateral metatarsals with curved shafts somewhat similar to 

 those in the manus. The ungual jihalanges are shorter than in the manus. 



The remains of Diceratherium cooki constitute by far the greatest percentage of 

 all the material found in the Agate Spring Fossil Quarries. Another significant 



* Pomel referred the species to Aceratherium. Professor Max Schlosser identifies it as Diceratherium 

 in the case of material sent to us from the Royal Museum in Munich. 



