PYROTHERIUM SORONDOI 175 
in lower jaw of P. sorondoi. P. plutewm is based on three 
lower teeth of smaller size than the typical P. sorondot, 
but the difference is small and there are no structural 
features accompanying it; so I consider it simply a smaller 
individual of P. sorondoi. In the generic discussion, 
Parapyrotherium planum was also assigned to P. sorondot. 
Pyrotherium romeri Ameghino 
P. romeri Amegh., 1889, Act. Acad. Nac. Cience. Cordoba, t. VI, p. 618. 
P. romeri Lydekker, in part, 1894, Anal. Mus. La Plata, Palaeontologia Argen., 
t. III, supplement, p. 4. 
P. romeroi Amegh., 1894, Bol. Inst. Geog. Argen., t. 15, p. 612. 
P. romeroi Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 442. 
P. romeroi Amegh., 1902, Anal. Mus. Nac. Buenos Aires, ser. 3, t. 1, p. 32. 
P. romeri Gaudry, in part, 1909, Anal. Paleontologie, t. 4, p. 21. 
This species is characterized by the presence of pm. 
t which is absent in other species. The tooth is of fair 
size, two-rooted, narrow in front and has a narrow rim of 
enamel around it; and measures 22 mm. long by 14 mm. 
wide. The second premolar is 30 mm. long by 33 mm. 
wide. A lower tush is also associated with these two teeth 
and is of smaller size than in the following species, being 
at the alveolus border 40 mm. by 29 mm. in cross section. 
Pyrotherium sorondoi Ameghino 
P. sorondoi Amegh., 1894, Bol. Inst. Geog. Argen., t. 15, p. 613. 
P. sorondoi Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 443. 
P. sorondoi Amegh., 1902, Anal. Mus. Nac. Buenos Aires, ser. 3, t. 1, p. 30. 
P. sorondoi Amegh., 1906, Anal. Mus. Nac. Buenos Aires, ser. 3, t. 8, p. 331- 
P, romeri Lydekker, in part, 1894, Anal. Mus. La Plata, Paleontologia Argen- 
tina, t. III, supplement, p. 4. 
P. romeri Gaudry, in part, 1909, Anal. Paleontologie, t. 4, p. 21. 
P, giganteum Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 447. 
P. crassidens Amegh., 1902, Anal. Mus. Nac. Buenos Aires, ser. 3, t. I, p- 34. 
P. planum Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 446. 
Parapyrotherium planum Amegh., 1902, Anal. Mus. Nac. B. A., ser. 3, t. 1, p. 29. 
P. trilophodon Amegh., 1902, Anal. Mus. Nac. B. A., ser. 3, t. I, p. 33- 
P. pluteum Amegh., 1901, Bol. Acad. Nac. Cienc. Cordoba, t. 16, p. 386. 
P. pluteum Amegh., 1902, Anal. Mus. Nac. Buenos Aires, ser. 3, t. I, p. 29. 
The species varies in size and in the proportionate 
development of the tushes as would be expected in a large 
