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 E. molaris the dental series is parallel to the external 

 border of the jaw; in E. latibuccatus the tooth line is deflected inwards 

 from the border, leaving a wide space. 



Empedocxes 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 is a 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 bones 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 basisphenoicl arises between the internal 

 angles of the pterygoids above mentioned, and ceases before reaching the 

 inferior border of the occipital condyle. The 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 Diadectidce, maybe due to the loss of the 

 basioccipital bone. It would be a remarkable coincidence if tliis 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. 



* Diadcctcs latibuccatus, Proceed. Amer. Philos. Soc, 1878, p. 505. 



