32 



THE DESEADO FORMATION OF PATAGONIA 



the astragulus developed in two planes so that it appears 

 as a deep notch. In the case, of the new genus the toes 

 are almost equal in size, giving us a stage in the develop- 

 ment of this three- toed form which is much more primitive 

 than the well-known Santa Cruz genus. 



Notodiaphorus crassus sp. nov. 



The specimen selected as type is number 3287 of the 

 Amherst Collection, consisting of a complete pes, tarsus, 

 lower end of the tibia, and the femur, 

 from the Deseado on the Chico del 

 Chubut River, west of Puerto Visser. 

 Beside this, there are seven other speci- 

 mens, mostly parts of hind limbs, but 

 others having also the lower end of the 

 humerus, the radius and ulna, metacar- 

 pals, and some phalanges. The species 

 is distinguished by its large size, being 

 larger than the species of the Santa 

 Cruz, and, at the same time, the three 

 Fig. 6. D^tai end of right toes of both the pes and the manus are 



humerus — 1/2 natural size. , ... 



subequal in size. 

 The distal end of the humerus associated indirectly 

 with this species is moderately heavy, with fair-sized epi- 

 condyles, and no entepicondylar foramen. The supratro- 

 chlear fossa is moderately deep, the anconeal very deep, 

 the two being connected by a small foramen, as is typical 

 for this family. The trochlearis, slightly oblique to the 

 long axis of the shaft, has a simple pulley-like articular 

 end without ridges of division, the internal border being 

 narrower and higher than the external. 



Measurements, Specimen 3201 



Humerus, greatest diameter of the distal end 



width of trochlea on the anterior side 

 width of trochlea on the posterior side 



58 mm. 

 37 mm. 

 28 mm. 



