212 B. NATURAL HISTORY. 
riorly a convexity to the tusk. The edge of the mandibular arch 
is correlated between these cutting edges, but its extremity is 
three-lobed. These lobes correspond to three grooves within the 
premaxillary portion of the edge of the jaw, which are separated 
by two ridges. The section of the tusks is cylindric, and where 
broken, at the alveolar margin, the pulp cavity is minute. 
The malar bone is small, and of a subtriangular form, one apex 
being posterior. The antero-superior angle extends to the lachry- 
mal, thus excluding the maxillary from the circumference of the 
orbit. 
The dentary bone extends far posteriorly, and forms the greater 
part of the circumference of a longitudinal foramen, which pierces 
the middle of the ramus. The angular is prolonged into a keel- 
like plate below, which is truncate behind, and rises gradually 
anteriorly. Its margin, which articulates with the articular, is cut 
out by a deep foramen. 
The angular and articular bones are both horizontal. The coro- 
noid appears to be broken off, interior, or wanting. The angular 
extends to the symphysis.* 
The palatal surface is not exposed. 
Affinities of the Anomodontia. 
The attachment of the os quadratum, with the Mammalian type 
of rib articulation, and the elongate sacrum, induced me to regard 
the Anomodontia as a subgroup of the Archosauria. The absence 
of the quadratojugal arch, usual in the latter order, and the lack 
of information respecting the mode of attachment of the os quad- 
ratum, rendered it probable that the group was aberrant, or even 
not properly referable to it. The extension of the exoccipital 
bones, so as to close the parieto-squamosal arch, is found among 
Lacertilia in the Stenodactylus guttatus, and a very few other 
species; but its extension to the quadratum below the proximal 
articulation does not occur. 
The immovable articulation of the quadratum throughout its 
length to the squamosal, and by its whole inner margin (as I 
suspect, but cannot see without too much injury to the specimen) 
to the exoccipital, removes the Anomodontia from the Lacertilia, 
and associates them with the Archosauria, in accordance with the 
indications furnished by the ribs, sacrum, etc. The withdrawal of 
* See Trans. Amer. Philos. Soc., 1869, pp. 27, 33. 
