320 THE AMERICAN NATURALIST. [VoL. XXXII. 
being bulbous, as in Tritylodon, covered by long nasals with 
a short free portion. Large lachrymals, and, conforming with 
the carnivorous habit and strong temporal muscles, there is a 
high sagittal crest, deep temporal fossæ and a strong, deep 
zygomatic arch, powerful chin and coronoid process (formed 
from the dentary). The serrated teeth agree in number with 
Osborn’s promammalian formula, consisting of four incisors, 
powerful canines, five pointed and basal cusped premolars, and 
four triconid molars. As in the Protodonta, the molar fangs 
are slightly grooved, indicating a division into two roots. 
There are also incipient traces of a cingulum (1895, 5, Fig. 2) 
and some evidence that there was a succession of the teeth 
Fic. 7. — Lateral view of the teeth of Cynognathus crateronotus, showing the five simple pre- 
molars and triconodont molars with grooved fangs. (4 natura! size. After Seeley.) 
(1895, 5, p. 62). All these are promammalian characters. A 
close approximation to this type is in the marsupial Triconodon 
of the Upper Jurassic. Professor Seeley has pointed out (1895, 
5,P- 90), also, that there exists a still closer resemblance between 
this type and Microconodon. 
A perforation behind the orbits, which Cope and Baur, and 
very recently Case,! have considered as possibly representing 
the infratemporal fossa, is regarded by Seeley as a vacuity. 
Upon page 74 (1895, 5) Seeley also compares this vacuity 
with the infratemporal fossa. According to this interpretation, 
the mammalian zygoma was originally a compound structure, 
composed of the squamosal + prosquamosal above and the 
quadratojugal below. A palate, formed apparently by hori- 
1 American Naturalist, February, 1898, p. 73. This paper contains a valuable 
critique of the same subject from the standpoint of the temporal arches. 
oe 
