1 64 THE DESEADO FORMATION OF PATAGONIA 



Pyrotherium Ameghino 



Pyrotherium Amegh., 1889, Actas Acad. Nac. Cienc. Cordoba, t. VI, p. 617. 

 Pyrotherium Lydekker, 1894, Anal. Mus. La Plata, Palaeontologia Argentina 



pt. 3, p. 4. 

 Pyrotherium Amegh., 1895, Bol. Inst. Geog. Argen., t. 15, p. 609. 

 Pyrotherium Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 441. 

 Pyrotherium Amegh., 1902, Anal. Mus. Nac. Buenos Aires, ser. 3, t. 1, p. 19-43. 

 Pyrotherium Amegh., 1902, Anal. Mus. Nac. Buenos Aires, ser. 3, t. I, p. 223-4. 

 Pyrotherium Gaudry, 1909, Anal. Palaeontologie, t. 4, p. 1-28. 

 Parapyrotherium Amegh., 1902, Anal. Mus. Nac. Buenos Aires, ser. 3, t. 1, p. 



29. 



The type species of the genus is P. romeri, which is 

 however a rare species, most of the material and the best 

 known belonging to P. sorondoi. The Amherst Collection 

 contains a skull, complete except that the top of the brain 

 case is crushed in and the parietals lost; a second skull 

 with the full upper dentition but lacking the cranium; 

 four lower jaws; two isolated tushes; the atlas, axis, and 

 crevicals 3 and 4; the humerus; the proximal end of the 

 femur; and part of the front foot; all from the Chico del 

 Chubut west of Puerto Visser. Gaudry had upper and 

 lower dentition and the fore and hind limbs except the feet. 

 Ameghino described the upper and lower dentitions and 

 a fore foot, so that with our material we now have a dasis 

 for a fairly complete discussion, the vertebral column being 

 the major part which is still lacking. 



The first striking feature is the dental formula. As 

 formerly given, it is inaccurate, there being two great 

 tushes on either side of the upper jaw, instead of one, as 

 described. At first sight, I thought it might be a meristic 

 variation, but both of my skulls show the same arrange- 

 ment on both sides, and these are the first two skulls 

 which have been found complete to the front end, and 

 neither is by any means a young individual. The dental 

 formula would then read \ ° \\ > 



Upper incisor 1 is a rootless, permanently growing tush 

 about a fourth smaller than inc. 2, but of the same 



