i I \K\V KKl'TII.KS AND STEGOCEPHALIAN8 llfo.M 



upper ex tre mity. The articular face for the lower jaw is convex antero-posteriorly and 

 divided into two parts by a sharp median elevation which runs obliquely from within 

 outward and backward. The suture with the quadratojugal is vertical and nearly 

 straight, running from the lower extremity of the bone nearly to the top. There is 

 a large quadrate foramen at about the middle point of the suture, which runs slightly 

 downward and forward. On the inner face there is a slight concavity just above the 

 articular surface and then a strong spout-like process, concave downward, which extends 

 forward for a short distance, but not nearly so far as is indicated by v. Huene in M. 

 phhiingeri. The inner edge of this process rises gradually, shortening as it rises, and 

 disappears on the anterior face of the quadrate at about the middle of its height. At 

 t he origin of this process and above and outside it there is a fairly deep pit. The posterior 

 edge of the quadrate process of the pterygoid fits over this process on the lower and 

 inner side. The upper portion of the outer edge of the quadrate is inclined inward 

 slightly, and the upper extremity terminates in a smooth, nearly hemispherical face 

 which fits into a pit on the lower surface of the squamosal. There can be no doubt 

 that there was a certain amount of motion possible at this point, which would be per- 

 mitted by the sliding of the quadrate process of the pterygoid on the spout-like process 

 of the quadrate. This reveals a greater flexibility of the posterior portion of the skull 

 of the Parasuchia than has previously been suspected. Versluys 1 regarded the skull of 

 the Parasucltin as akinetic, but there is a possibility of movement between the parietal 

 and supraoecipital and a possibility of movement of the pterygoids on the basipterygoid 

 processes of the basisphenoid ; these possibilities, taken with the evidence of the movable 

 quadrate and the smooth face between the pterygoid and the transverse, indicate that 

 the skull of the Parasuchia was certainly kinetic. 



The lower surface of the skull. — In this portion of the discussion is included the 

 description of the walls of the brain-case and the narial region. 



The basioccipital-basisphenoid. — On the lower surface the basioccipital differs 

 decidedly from specimens Nos. 7261 and 7505, described on a later page. In these 

 specimens the lower surface of the neck of the condyle is smooth and rounded, without 

 any ridges running forward to the tubera basioccipitalia. In No. 7522 the lower surface 

 of the neck is flat, with two prominent rounded ridges on the sides of the neck running 

 from the condyle to the tubera. This forms a decided concave area with a nearly flat 

 bottom, but a little more depressed on the sides. A similar condition is indicated in 

 the imperfect specimen, No. 7474. 



The tubera are prominent and formed by the basioccipital and basisphenoid. 

 The basipterygoid processes are well formed and project outward, downward, and 

 forward; at the posterior end of each there is a sharp, low prominence; such prominences 

 are described in No. 7257, and their position is indicated in the other specimens by more 

 or less evident areas of slight rugosity. The space between the basipterygoid processes 

 is occupied by a low, sharp ridge which is continuous with the very sharp lower edge 

 of the parasphenoid rostrum. This condition is quite different from the other spec- 

 imens. In No. 7257 the space is occupied by three ridges; the middle one, somewhat 

 asymmetrically placed on the right side, was probably continuous with the lower edge 

 of the parasphenoid rostrum; in No. 7261 there are faint ridges on each side and no 

 median ridge; in No. 7505 there IS the faint beginning of a median ridge: in No. 7474 

 the region is not preserved. 



The parasphenoid rostrum start- to rise almost directly upward in the skull; the 

 proximal portion of the lower edge is nearly at right angles to the line of the basicranial 

 •i x i ~. hut quickly assumes a horizontal position. The lower edge is very sharp. There 



1 Veruluys, J., ZoologischtT Jahrbuch, tupplemenl xv, 2 Band, i. 847, 1012. 



