688 THE BKIDGER FAFNA. 



two lateral supraoccipital crests, which contract as they descend, and con- 

 tinue to the extremities of the post-tympanic processes. Although the post- 

 orbital angles are prominent, they cannot be called processes. The paroc- 

 cipital processes are large, and are directed vertically downwards. They 

 are separated by the usual concavity from the occipital condyles. The 

 posttympanics are very short, forming only an angle projecting downwards 

 at the anterior base of the paroccipitals, from which they are only separated 

 by a notch. The inferior side of the tympanic bone is flat near the meatus, 

 but opposite the stylomastoid fossa its posterior border is turned forwards,, 

 and is produced into a well-marked process. It incloses a groove in front 

 of it, which is continuous with the pterygoid fossa. The petrous bone is 

 not inflated, and its inferior surface is divided into two longitudinal ridges. 

 The inner is the less prominent, and is in close contact with the basioccipi- 

 tal. The postglenoid processes are robust and obtuse. The basioccipital is 

 excavated in front of each of the condyles. The inferior surface is nearly 

 flat, with a slight median keel. The pterygoid fossa is Avell defined, and is 

 long and narrow. The posterior nareal trough is elongate, the descending 

 pterygoid processes of the sphenoid originating as far back as the apex of the 

 OS petrosum. This species is especially characterized by the presence of an 

 acute keel like ridge, which extends horizontally above the foi'amina spheno- 

 orbitale and opticum, and turns upwards anterior to the latter, terminating 

 a half inch below the inferior base of the postorbital process. All the fora- 

 mina are below it, but there is a fossa above it, opposite the interspace be- 

 tween the / opticum and / sphenoorhitale. 



A supraorbital foramen pierces the frontal bone a quarter of an inch 

 within the superciliary border. There are five or six postparietal foramina, 

 two of which are nearly on the squamosal suture There is a postsqua- 

 mosal foramen, and also a not very small supraglenoid foramen. There is 

 a small foramen anterior to the optic, and in line with the posterior part of 

 the postfrontal angle. The foramen opticum is large, and is 10™". in front 

 of the / sphenoorhitale. The latter is separated by a lamina from the large 

 and vertically oval / rotundum. The latter is joined by the large alisphenoid 

 canal, whose posterior orifice is as large as the foramen ovale. The latter 

 is large, and is well separated from the / lacermn anterius. The / / lac.era 



