SCOTT: TOXODONTA OF THE SANTA CRUZ BEDS. 
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the hinder ends of the nasals, these processes are always much shorter and 
narrower than in Nesodon, though of similiar triangular shape. More 
commonly, however, there are no such processes and the anterior border 
of the frontals is deeply emarginated to receive the nasals in a concavity. 
According to Ameghino (’94*, 245) the skulls which have triangular pro- 
cesses of the frontals between the hinder ends of the nasals are the most 
abundant, but this is certainly not true of the Princeton collections. 
The nasals are long and narrow, slightly convex antero-posteriorly and 
strongly so in the transverse direction ; anteriorly, their projection in front 
of the premaxillae is rather shorter proportionately than in Nesodon , giv- 
ing a slightly different shape to the narial opening. Posteriorly, there 
are considerable differences among the various skulls in the form of the 
nasals, differences which Ameghino has employed for taxonomic purposes 
('94 / ', 245; ’07, 65, ff. ), though the variability is such that the taxonomic 
importance of these characters is very doubtful. Four different types 
may be distinguished in the form of the hinder ends of the nasals and in 
the consequent character of the fronto-nasal suture. (1) The nasals are 
of almost uniform width from end to end and are simply rounded pos- 
teriorly; (2) they are suddenly narrowed at the contact with the frontals 
and make the fronto-nasal suture almost triangular ; (3) they gradually 
narrow backward from the frontal contact and the frontals are less deeply 
emarginated than in the preceding types. (4) In the first three types the 
two nasals are in contact with each other throughout their entire length, 
while in the fourth their posterior ends are separated by small nasal 
processes of the frontals, as above described. Other slight differences, 
probably individual, though perhaps specific, may be noted in the shape 
of the nasals. Usually, these bones are of nearly constant width, with a 
very shallow constriction near the middle of their length and broadening 
slightly in front of and behind the constriction. In some cases, however, 
the bones are widest near the middle, contracting toward the ends, but 
the difference is by no means striking. 
The premaxillae differ hardly at all from those of Nesodon; the ascend- 
ing ramus is somewhat broader antero-posteriorly in proportion to its 
height dorso-ventrally and its anterior free border is more vertical, form- 
ing a more definite angle with the horizontal ramus. The spine-like 
rugosities which arise from the antero-dorsal angles of the horizontal 
rami are rather less conspicuous than in the larger genus. The maxil- 
