SCOTT: ENTELONYCHIA OF THE SANTA CRUZ BEDS. 
253 
speedily disappears with wear. The posterior crest is much shorter and 
the notch between it and the outer wall is much deeper, but it also is 
soon destroyed by abrasion. 
Presumably, it is to the presence of these notches that Ameghino refers 
when he says: “Cette denture est en realite buno-lophodonte, les deux 
lobules internes des molaires superieures (protocone et hypocone) restant 
longtemps separes en forme de tubercules pointues” (’94*, 56). This 
statement is quite erroneous, as immediately appears when the upper 
molars of Homalodontotherium are compared with those of the titano- 
theres, which family has truly buno-lophodont teeth. Disregarding the 
peculiar character of the external wall in this family, which it shares with 
the horses and the palaeotheres, we find that there in no indication of a 
transverse crest in the titanotheres, the internal cusps being altogether 
distinct and of conical shape. In some of the Eocene genera more or 
less definite remnants of the conules may be found, but there is no 
tendency for these conules to coalesce with the inner cusps. In the 
Santa Cruz genus, on the contrary, there are well defined transverse 
crests, which are partially separated from the outer wall, in the unworn 
state of the teeth, by shallow notches, which are soon obliterated by wear. 
Fig. 43. 
Homalodontotherium segovice : Second and third upper molars of left side, X y- Oblique view 
of grinding surface. M- slightly worn, m- not yet erupted. (No. 16,014.) 
In m- a thin, almost plate-like ridge runs obliquely forward from 
the isolated apex of the posterior crest, dividing the valley into two por- 
tions, a deep internal and shallow external part. Besides, two short 
spurs are given off inward from the external wall and, with the ridge just 
mentioned, enclose two shallow fossae. After a short period of use, how- 
