1885.J 2o5 LCope- 



the probable alisphenoid, whose posterior edge is nearly parallel with the 

 anterior border of the prootic, sloping forwards as it descends. Tbe basi- 

 cranial axis is thin at their union on the middle line below, and, thickening 

 forwards, is excavated by rather small conical fossa. Anterior to the fossa 

 is a smaller impressed fossa, and on either side of it, each lateral wall is 

 excavated into a shallow fossa wbich descends towards it. The frontopa- 

 rietal fontanelle is of extraordinary size. 



1. The Brain. 



Wben the superior border of the medulla oblongata at the foramen mag- 

 num is placed horizontally, the axis of the brain ascends at an angle of 

 45° towards the frontoparietal fontanelle. The superior surface, anterior to 

 the foramen magnum, is subquadrate in outline, the angles being trun- 

 cated, and directed anteriorly, posteriorly and laterally. A posterior con- 

 striction connects it with the medulla ; and an anterior one defines the 

 middle brain and hemispheres. Each lateral truncated angle represents 

 the foramen of the trigeminus nerve. The space thus bounded is divided 

 into two nearly equal areas by a transverse groove, which extends from the 

 posterior edge of one of these foramina to the other. The posterior of these 

 I suppose to represent the cerebellum, and the anterior the optic thalami. 

 The cerebellar surface indicates that, as in many lizards, the cerebellum is 

 simple, and very slightly convex. 



Anterior to the foramen trigemini, the brain contracts so as to have a 

 transverse diameter scarcely more than one-third its vertical diameter. 

 The cast at a point twice as far in advance of the cerebellar line as the fore 

 and aft width of the cerebellum, rises to fill the frontoparietal foramen, 

 forming a mass which represents the huge pineal sac or epiphysis. The 

 proportions of this body are even greater than they are in any of the exist- 

 ing Lacertilia, and it has a greater transverse diameter than the middle 

 brain inferior to it. Its posterior border is at right angles to the line con- 

 tinued forwards from the superior border of the medulla oblongata at the 

 foramen magnum. At its posterior base a flat horizontal process, as wide 

 as the brain at this point, extends posteriorly in a corresponding fossa of 

 the superior cranial wall. Its posterior margin occupies a transverse 

 groove of the superior wall between the superior and inferior plates. 

 Each lateroposterior angle is produced, and may represent the foramen of 

 exit of a narrow canal which appears to perforate the lateral wall and issue 

 beneath the roof of the temporal fossa. A larger projection of each side of 

 the base of the epiphyseal mass occupies a large foramen of the lateral wall, 

 which has the superior wall for its superior border. This may only repre- 

 sent a vacuity of the wall, but the fossa at the posterior base of the epi- 

 physis has greater significance. What this is I am at present unable to 

 ascertain. 



Below the epiphysis the transverse diameter of the brain is about one- 

 fourth the vertical, not including a short inferior prominence. The latter 

 is small and conical, and is situated below the center of the epiphysis 



