284 Dr. B. Petronievics on the 
with the forward process of nasals (or, perhaps, with part of 
the ossified internasal septum) from above, so that the bone 
Fig. 1. 
$a. 
ee 
~ 
eee eee 
oe OF} Sse 
~ 
~ 
=- 
Skull of Tritylodon, upper view, 2 nat. size. , probable sutures ; 
—.-.-, possible suture (between fr. and prfr.); ----, restored parts. 
pa., parietal; sg., squamosal; 7u., jugal; fr, frontal; prfr., prefrontal ; 
le., lacrimal; na., nasals ; mz., maxillary ; smz., septomaxillary ; 
pmxz., premaxillary; pr.pmx., process of the premaxillaries ; 
a.°, second upper incisor. 
vertically separating the two nares seems to be composed of 
these two parts. Between the front part of premaxillaries 
