10 
buccatus.* The latter is represented by portions of two mandibles in my 
collection ; the former by two or three skulls, with part of the mandible 
accompanying one of them. The difference in the forms of the mandibles 
is well marked. In #. molaris the dental series is parallel to the external 
border of the jaw; in H#. latibuccatus the tooth line is deflected inwards 
from the border, leaving a wide space. 
EMPEDOCLES MOLARIS Cope. 
Diadectes molaris Cope. American Naturalist, 1878, p. 565. 
The molar teeth are wider in this species than in any species of the 
family yet known. The internal and external extremities of the crown 
are about equally wide and equally elevated, and there isa low median 
cusp. A portion of the grinding surface both internal and external to the 
cusp is horizontal ; the surface of this portion is wrinkled. The last molar 
is smaller than the others. The inner border of the maxillary benes forms 
a curved ridge on each side of the palate, which is separated by a groove 
from the vomer. The latter forms a median keel at the anterior portion of 
the palate, where it supports two rows of small conical teeth. The palatines 
have their prominent internal edges juxtaposed as far as the transverse line 
of the last molars. There they diverge a little, and extend as two nearly 
parallel keels to a prominent angle on each side, opposite the middle of the 
zygomatic foramen. There the inner borders cease to project, and are 
directed obliquely outwards to the inner extremities of the quadrate bones. 
The external borders of the pterygoids are more elevated than the inter- 
nal. The median keel of the basisphenoid arises between the internal 
angles of the pterygoids above mentioned, and ceases before reaching the 
inferior border of the occipital condyle. Tbe external border of the ex- 
occipital is sigmoidally flexed. 
It has occurred to me that the peculiar condition of the occiput described 
under the head of the family Diadectide, may be due to the loss of the 
basioccipital bone. It would be a remarkable coincidence if this accident 
should have befallen the only three crania which have come into my pos- 
session. 
The anterior border of the orbit is above the anterior part of the fourth 
molar, counting from behind. The distinct incisive foramina are longitudi- 
nal and rather large. The anterior border is opposite to the fourth tooth 
counting from the first incisor. The nostrils look out laterally and a little 
forward ; the united spines of the premaxillaries form a stout septum. 
The incisors are not more than three or four on each side (I cannot find the 
premaxillo-maxillary suture), and they form a regularly convex series. 
With the maxillaries, the entire dentition of one side forms a gentle sig- 
moid curve. The median incisors are the largest ; the sizes regularly di- 
minish until the smallest are reached on the anterior part of the maxillary 
bone. Posterior to this point they enlarge again. Their apices are not 
preserved. : 
* Diadcctes latibuccatus, Proceed, Amer. Philos. Soc., 1878, p. 505. 
