Fig. 48. E. spegazzinianus, right upper dentition—
natural size.

The arrangement of the teeth of the lower jaw is shown in [fig. 25 h]., after Ameghino. The first and second incisors are greatly enlarged. Incisor 3 is lacking, and the canine vestigal. Pm. 1 is small and single-lobed, the succeeding premolars and molars being large and divided into two lobes by a deep external, and a shallow internal infolding.

Measurements
Skull, width between the orbits 60 mm.
Skull, width between the orbits 60 mm.
Skull, width across the postorbital processes 88 mm.
Skull, height from m. 2 to top of frontal 77 mm.
Skull, width of palate opposite inc. 2 42 mm.
Skull, width of palate opposite m. 2 62 mm.
Dentition,length inc. 1 to m. 3140 mm.
Dentition, incisor 1 ant.-post.length 11 mm.width  16 mm.
Dentition, pm. 3length 11 mm.width  13 mm.
Dentition, m. 2length 22 mm.width  16 mm.

Eutrachytherus conturbatus Ameghino

Trachytherus conturbatus Amegh., 1895, Bol. Inst. Geog. Argen., t. 15, p. 623.
Eutrachytherus conturbatus Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 429.

This species is founded on upper teeth, which are said to be relatively smaller anteriorly, and actually smaller throughout, by about 15% than are those of the preceding species. Molar 1 measures 17 mm. long by 9 mm. wide.

Eutrachytherus grandis sp. nov.

This species is based on upper molars 1 and 2 of the left side, from the Deseado beds, of the Chico del Chubut, west of Puerto Visser. The teeth are typically those of the genus and differ only from other species in their large size, being some 50% larger than the corresponding teeth of E. spegazzinianus. Each is covered with a layer of fully half a millimeter of cement.

Fig. 49. E. grandis, molars of the left side—
natural size.