30 NEW REPTILES AND STEGOCEPHALIANS FROM 



where the smooth area permits the most careful examination. This smooth area is 

 the surface of a shallow depression which runs directly across the top of the skull, from 

 a point opposite the anterior half of the upper edge of the temporal opening to the same 

 point on the other side; its posterior border is somewhat sharply elevated by the 

 rugosity of the surface of the squamosal and parietal bones, and it is divided by a low 

 ridge on the median line of the skull. The most of the upper surface is so deeply 

 sculptured that the sutures are not visible, but it appears from the arrangement of the 

 sculpture that the frontals, paired or unpaired, occupy a heart-shaped area from about 

 the posterior line of the orbits as far forward as the nasals. There is, on each side, a 

 deep groove or elongate pit just within the very rugose upper border of the orbit. At 

 the posterior inner edge of this groove there is the center of rugosity which may mark 

 the anterior inner corner of the postorbital. 



The posterior face of the skull (fig. 7 c and plate 5 d). — This face of the skull was 

 readily freed from the matrix and presents a smooth surface of uninjured bones, upon 

 which no marks or sutures could be missed. The whole face is semicircular, with the 

 prominent occipital condyle in the center of the horizontal lower edge. The surface 

 is completely closed, with the exception of the post-temporal openings (which are so 

 small as to be reckoned as little more than foramina) and the large foramen magnum. 

 In the median line above there is a thin but prominent ridge flanked by vertically 

 elongate pits. The whole surface slants backward at a slight angle and is concave 

 from side to side above the line of the opisthotics; below this line the distal ends of the 

 opisthotics slant more acutely backward, increasing the concavity. The line of division 

 between the opisthotics and the plate above is traceable inward for a short distance 

 beyond the post-temporal openings; the sutures between the exoccipitals and the ad- 

 jacent elements are completely obliterated. Just above the foramen magnum there are 

 small prominences which suggest the presence, in the complete skeleton, of a proatlas. 

 The opisthotics turn sharply outward from their junction with the exoccipital portion; 

 their posterior faces are smooth, with a low ridge which runs outward and slightly 

 downward on the inner half. The distal portion is slightly expanded and the fairly 

 broad, somewhat triangular distal ends are visible from the rear. 



Between the distal end of the triangular terminal face of the opisthotic, which 

 points forward, and the quadratojugal there is visible a wedge-like surface of bone 

 which must be a portion of the nearly concealed quadrate. There is no trace of a quad- 

 ratojugal foramen. The occipital condyle is nearly spherical and is supported upon 

 a well-defined neck; there is no trace of a pit marking the forward extension of the 

 notochord. A distinct line marks the contact of the posterior plate of the skull with 

 the squamosal-quadratojugal; the plate sends a long process to fill the space between 

 the distal end of the opisthotic and squamosal-quadratojugal. 



The lower surface of the skull (fig. 7 d and plate 5 c). — The pterygoids and the bones 

 of the palatal region are, most unfortunately, absent, but the bones of the brain-case 

 are so perfectly preserved that all the foramina can be made out; the sutures are all 

 closed and can not be traced. The phytosauroid characters are seen in the prominent 

 basioccipital-basisphenoid mass lying well below the level of the occipital condyle, in 

 the deep pit which lies in the usual position of the openings of the Eustachian canals, 

 in the strong basipterygoid processes of the basisphenoid, and in the strong alisphenoids 

 rising to the roof of the skull and firmly attached to it. The primitive character is 

 shown in the evident loose attachment of the pterygoids and the prominent, free, 

 parasphenoid rostrum. 



The basioccipilal.— Anterior to the condyle the lower surface of the bone bends 

 sharply downward and forms, or approaches close to, the posterior edge of the deep 



