18 



outwards, and follows closely the maxillary bone well posteriorly. It then 

 turns inwards, extending to the parasphenoid bone, with the wide portion 

 of which it has an extensive contact. It then turns outwards as pterygoid 

 bone, and rapidly narrowing, joins the inner distal extremity of the quad- 

 rate. It thus encloses a foramen with the quadratojugal bone, which is 

 much smaller than the choanoorbital foramen. The posterior part of the 

 inferior surface of the bones of this arch, not including the slender ptery- 

 goid portion, is roughened with hard nodules resembling teeth in material, 

 and serving the purpose of such organs. 



Two rod -like bones extend outwards and backwards fr@m the posterior 

 part of the parasphenoid and the basioccipital, which belong to the inferior 

 arches. The anterior is the larger, and is bent backwards at an obtuse 

 angle ; its proximal extremity is a truncate oval. This bone occupies the 

 position of the stapes. The second is extensively in contact with the basi- 

 occipital by its proximal extremity. It is curved backwards at its distal 

 third. The occipital condyle is represented by a fish-like cotylus, which 

 has a deep notch at its superior border. 



The mandible has a short angular process, vertical by lateral compres- 

 sion. The symphysis is very short and the Meckelian cavity large, and 

 completely enclosed. 



The anterior cervical vertebra? consist of the same elements as the dorsals. 

 The intercentra of the second and third vertebrae support capitular costal 

 articulations, somewhat elevated above the surrounding level. The pleuro- 

 centra do not support the ribs, but the neural arches terminate below in 

 diapophyses. There is a pleurocentrum in front of the second intercentrum, 

 and above and in front of it a neurapophysis, which has no distinct diapoph- 

 ysis. Its superior portion is a subacute process which is not in contact 

 with that of the other side, but is separated from it by a vertical osseous 

 plate, which is probably the neural spine of the second vertebra or axis. 

 This is similar to. the structure already observed in Eryops, and the parts 

 being in place, should explain those of that genus. The portion of the 

 atlas which represents the intercentrum is divided into two lateral portions, 

 each of which has the form of an entire intercentrum, i.e., crescentic. 

 The intercentrum of a cervical of a large species of this group, is wider 

 than that of the other vertebra, and presents two articular facets anteriorly. 



Specific Characters. — The skull is flat and rather wide, the length ex- 

 ceeding a little the transverse posterior diameter. The posterior borders 

 of the orbits mark a point half way between the extremity of the muzzle, 

 and the posterior supraoccipital border. The orbits themselves are of 

 medium size, and are separated by a space about equal to their transverse 

 diameter. Their form is a wide oval, with the long axis obliquely antero- 

 posterior. The diameter of the external nostril is nearly half that of the 

 orbit, and the form is similar to that of the latter. The interorbital and 

 ethmoid regions are concave ; the prefrontal regions are convex. The su-. 

 preoccipital border is strongly concave ; and the notch separating the 

 cpiotic angle from the quadrate angle is as deep as the supraoccipital. The 



