380 Bulletin American Museum of Natural History. [Vol. XXVIL, 



The interlocking narrow carpus of the Perissodactyls, as we know them, is a 

 very constant character (p. 393), while there is some reason to suppose that 

 in the Condylarths the differentiation of the serial and interlocking types 

 was at first almost nil, and long remained inconstant. It is of course under- 

 stood that when the Typotheres, Litopterns, etc., are hypothetically derived 

 from the Condylarthra it is meant only that the supposed common ancestors 

 of the South American series would probably resemble Euprotogonia in 

 some respects, MeniscotJirrium in others, and would thus fall within the 

 order Condylarthra. 



The Pjiroflieria^ (Lnccrto' Sedi.'i).- 



Pi/rotlierium is not the least puzzling of the curious extinct Patagonian 

 Ungulates. Its up})er and lower cheek teeth are of the bilophodont type, 

 that is, with two straight cross crests, and they are at first sight so much like 

 those of the Miocene proboscidean Dinotheriiim of Europe that Dr. Fl. 

 Ameghino {e. g., 1902, pp. 223-224), the original describer of Pijrotherium, 

 has regarded it as an ancestral proboscidean. It has also a single pair of 

 procumbent lower incisor tusks which grew continuously and had the enamel 

 band confined to the anterior surface, as in rodents and early proboscideans; 

 while the manus ascribed to it by Ameghino, but later declared by M. 

 Tournouer to belong to Astrapotherium, certainly resembles in most charac- 

 ters the ])roboscidean type. 



Fragmentary remains of the genus under consideration are characteristic 

 of the so called '' Pyr other ium beds" of Chubut and Deseado. The age of 

 these beds is very differently estimated by the leading authorities. Ame- 

 ghino places them in the uppermost Cretaceous, but the majority of northern 

 ])aleontologists, including INI. Gaudry, are unwilling to concede that the 

 Pyrotherium beds are older than the INIiddle Eocene. 



M. Gaudry's material, although by far the most complete so far collected, 

 still leaves us with a very imperfect knowledge of the skull and feet; but it 

 includes specimens in an excellent state of preservation of the following 

 ])arts: the upper and lower- jaws, \\iX\\ the milk and permanent dentitions, 

 the atlas, axis, a cervical vertebra, a lumbar, a caudal, the lower part of the 

 scapula, and a part of the ilium, a sternal bone, and fore and hind limbs 

 complete except for the manus and pes, which are represented only by a 

 lunar, cuneiform carpi, astragalus and cuboid. 



INI. Gaudry's oljservations upon the special characters of Pyrotherium 

 mav be summarized briefly as follows: The dentition diflfers in important 



1 The following section is partly quoted from a review by the writer (1909) of tlie late 

 Professor Gaudry's memoir on Pyrotherium (1909). 



