42 



THE DESEADO FORMATION OF PATAGONIA 



complete, and the right hind limb complete except for 

 the femur. In general, the animal is about f- the size of 

 Theosodon garrettorum, but in parts varies 

 from this as follows. The lower jaw is |, 

 the vertebrae are | in length, the hind leg 

 is 5 in length but f in diameter of bones, 

 while the metatarsus is only -3 in length. 

 This makes an almost plantigrade form of 

 heavy, clumsy proportions. 



Of the upper dentition we know only what 

 Ameghino has given us. The molar is distinguished by 

 the presence of both the protoconule and metaconule, by 

 the development of the posterior cingulum and by the 

 presence of three external styles. 



Fig. 14. Upper mo- 

 lar. 2 of the right 

 side — natural size, 

 after Ameghino. 



Measurements 



Upper premolar 4, length 12 mm., width 15 mm. 

 Upper molar 2, length 14 mm., width 17 mm. 



In the lower dentition, none of the teeth are reduced, 

 and all are in a continuous series, except that there is a 



Fig. T5. Right lower dentition — natural size, 



small diastema either side of pm. I. The incisors are 

 simple, compressed teeth, with but a trace of a cingulum. 

 The canine is incisiform and a trifle larger than the incisors. 

 Premolar 1 is also incisiform, and is isolated by a small 

 diastema on either side. The second premolar is longer 

 and wider than the first, and begins to show molariform 

 characters, the anterior portion being composed of a high 

 compressed cusp, the posterior portion by a low crescent 

 on which but one cusp is fully developed. The third pre- 

 molar is composed of two complete crescents, and has the 



