RHYNCHIPPUS 95 



gulus, and on the distal end a flattened slightly concave 

 facet for the calcaneum. 



The calcaneum is longer than in Nesodontidae. It is, 

 however, heavy and stout, the tuber broadening slightly 

 toward the free end, on the plantar side of which there is a 

 tendinous sulcus as in Nesodon. The fibular facet is wide, 

 rectangular, and convex. Of the astragular facets, the 

 sustentacular extends well back onto the tuber, and the 

 ectal is the usual ovoid surface. Distally there is a broad 

 slightly concave facet for the cuboid, and external to this 

 a narrow surface for contact on the navicular. Except in 

 length, this bone is very like that of Adinotherium. The 

 astragulus and rest of the tarsal bones are wanting. Parts 

 of the metatarsals and a phalanx indicate that the hind 

 foot is of the same tridactyl type as the front, differing 

 only in that the median digit seems to be relatively a little 

 heavier. 



Ameghino described three species of Rhynchippus, R. 

 equinus, R. pumulis, and R. medianus. 



Rhynchippus equinus Ameghino 



R. equinus Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 463. 



This species is the dominant one in the Deseado from 

 the Chico del Chubut, west of Puerto Pisser, no less than 

 fourteen individuals being represented in our collection, 

 three by skulls, and one by the major part of a skeleton 

 which was found associated with the skull of Leontinia, 

 but was determined as belonging to this species, by the 

 duplication of the radius with a specimen having the radius 

 and lower jaws associated. The description of the generic 

 characters is largely based on this skeleton. The three 

 species are differentiated largely by their size, R. equinus 

 being the largest, but as compared with R. pumulis it is 

 not only larger but much heavier built. 



The skull has been described under the generic discus- 

 sion. In young individuals, the furrow in the incisors and 



