392 ON A FOSSIL CALVARIA, 



papers read. 



On a Fossil Calvaria. 

 By Charles W, De Vis, B.A. 

 Plate 17. 

 A model of the upper surface of a brain, produced from the 

 interior of a fossil brain-pan, has already been under the inspection 

 of the Society. To obtain a just conception of the animal 

 represented by it, it appears necessary that the mould itself 

 should be brought into view. I therefore allow myself the 

 pleasure of submitting to consideration a cast of the entire fossil, 

 and of offering some remarks upon it for the purpose of eliciting 

 opinion. The portion of skull which time has left to us 

 consits of the parietal and the upper part of the occipital bones. 

 On its superior surface the sagittal suture is almost effaced — 

 it is indicated merely by a slight groove anteriorly. Posteriorly 

 there is a shallow depression between the particles immediately 

 in front of the superoccipital and from the radiated arrange- 

 ment of the cell-walls standing out in low relief from the 

 surface of the bone I am inclined to think that there is here an 

 interparietal ossified from a single centre. The parietals are flattened 

 anteriorly and gradually become very moderately convex posteriorly. 

 The cristas are far removed from the sagittal suture, and are 

 scarcely appreciable— mere linese temporalis from which the 

 temporal surfaces slope at a slightly increased angle. The occipital 

 surface makes with that of the parietals an open angle of 1 20°. 

 The lambdoidal suture is entirely effaced, but no superior occipital 

 crest is developed. A strong and prominent longitudinal spine 

 indicates the necessity that existed for a powerful ligamentum 

 nuchse. On each side of its upper half a large and deep impression 

 roughened by plate-like bony processes attests the volume of the 

 complexi. The longitudinal spine is crossed by a faint inferior 

 ridge, and beneath the crucial spine so formed there is an ample 

 smooth area on either side for the insertion of the deep muscles of 

 the neck. The confluence of the constituent bones of the calvaria 

 renders it a solid mass of great density and thickness. Measuring 



