52 NEW REPTILES AND STEGOCEPHALIANS FROM 



in this place and is filled with matrix, but an examination of the depression shows that 

 the edges of the pieces are sharply fractured and that there is no surface leading down 

 into a pit. The basipterygoid processes are prominent, extend slightly forward as well 

 as outward, and terminate in slightly convex faces. The parasphenoid process is of 

 remarkable length, extending forward for 75 millimeters. It gradually contracts ante- 

 riorly to a very thin lower edge. The sides of the process are flat, about 20 millimeters 

 high at the posterior end, and contract to not over 5 millimeters at the anterior end. 

 There is no indication of a division into upper (presphenoid) and lower (parasphenoid) 

 portions. 



The opisthotics are indistinguishable from the exoccipitals; they extend outward 

 and backward. The proximal portion of the complex is thick, but the distal portion 

 contracts to a thin oval, with the major axis placed vertically. To the outer, i. e., 

 toward the quadrate, side of the extremity of the right opisthotic there is attached a 

 small fragment of bone of irregular form. This was at first regarded as a displaced 

 fragment of no significance, but the extremity of the opisthotic of the opposite side shows 

 a sutural surface in the same position. The fragment is in exactly the position where 

 McGregor found a small element in Mystriosuchus 1 which he considered to be calcified 

 cartilage and identified as a hyoid element. 



The stapes. On the lower side of the right opisthotic there is preserved a portion 

 of a very slender stapes apparently in position. The portion preserved is about 1.5 

 centimeters in length, with a diameter of less than 1 millimeter. The outer extremity 

 is lost, but the inner end is evidently in place in the fenestra ovalis; the crushed condition 

 of the specimen in this region renders it impossible to determine the exact relations of 

 the inner end. 



The quadratojugal and the jugal are represented on the lower surface by their thin 

 lower edges only. 



The pterygoids. These bones are badly broken, but the parts are sufficiently well 

 preserved on the right side to permit a restoration of a major portion of the bones. The 

 articulation with the basipterygoid process of the basisphenoid is accomplished by a 

 well-formed, slightly concave facet on the inner edge of the bone, which is slightly 

 thickened at this point. The quadrate process extends backward, with a narrow, 

 concave face presented downward, which rapidly contracts toward its distal end. 

 As this face contracts, the body of the process assumes a vertical position. Union with 

 the quadrate is accomplished by a definite suture with the slender pterygoid process, 

 which is of considerable vertical extent. The external process of the pterygoid extends 

 outward almost at a right angle from a point a little in advance of the basisphenoid 

 process. The external process is not greatly thickened, but the posterior end descends 

 somewhat abruptly from the palatal surface, and from this point the bone slants gently 

 forward and upward. The posterior edge is thin and the outer corner is nearly a right 

 angle; the outer border descends rather sharply beneath the transverse. The anterior 

 process is broad posteriorly and contracts anteriorly as its inner edge is cut out by the 

 development of the interpterygoid vacuity. This portion of the bone is very thin and 

 much has been crushed and lost; the outline of the interpterygoid vacuity as represented 

 is uncertain, but enough can be made out to show that it was elongate, broader posteriorly, 

 and gradually contracting in front until the bones of the two sides met near the anterior 

 end of the parasphenoid process. The suture with the palatine is obscured, as the latter 

 bones are somewhat overthrust on both sides. 



The transverse is thin throughout ; its posterior end is expanded and fits closely over 

 the lower face of the outer part of the external process of the pterygoid; the inner edge is 



1 McGregor, J. H., Memoirs American Museum Natural History, vol. ix, pt. 11, 1906, pi. VH. 



