P. giganteum Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 447. P. crassidens Amegh., 1902, Anal. Mus. Nac. Buenos Aires, ser. 3, t. 1, 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. 1, 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. 1, p. 29. [Illustration: Fig. 111. Top of the skull—⅕ natural size; Mate to in 1 on the left side is represented by an alveolus but the tooth had fallen out before the death of the animal; _a.c._, ear chamber; _B_, brain case; _V_, vacuities in the bone.] [Illustration: Fig. 112. Side view of the skull—⅕ natural size, _i.1_, incisor 1 in outline restored from the right side; _i.2_, incisor 2; _J._, jugale; _M.1_, first molar; _Mx._, maxilla; _pm.2_, second premolar; _pmx._, premaxilla; _Pt._, pterygoid; the dotted line indicates position of nasal and frontal which are crushed down in specimen.] The species varies in size and in the proportionate development of the tushes as would be expected in a large and slow-growing animal. Most all of the material found by any of the collectors falls clearly into this species. Our specimens all came from the Chico del Chubut, west of Puerto Visser, which point is about 250 miles north of the locality where Gaudry’s material was found. The general features of the skull have been given under the generic description. The difference between this and the preceding species lies in the absence of pm. 1, and the somewhat larger size. Both of our major specimens are mutilated in places; and as the better skull was found with only the zygomatic arch exposed, we conclude that the parts missing were lost before burial. On the lower jaw the edges of some of the teeth were cracked off, and both the ascending rami are lacking, both things having happened before burial, this specimen being found well in the bank and never exposed to weathering. It appears as if the carcasses of the animals lay some time before being buried by the sediments. The scattered condition of all the finds indicates the same thing. The head of our femur is still marked by the teeth which cleaned the meat from the bone. The frequency of isolated tushes indicates that many jaws originally containing them have been either chewed to pieces or weathered away before burial. I do not think all the tushes found originally belonged to the lower jaw (Gaudry reports 18 tushes, all lower); for the upper and lower tushes when isolated are so much alike that it is difficult to distinguish them. The size of the skull is indicated by the following measurements: SPECIMEN NO. 3207