22 Mr. H. G. Seeley on the Structure of 



hind, but is free from investing phosphate, and so shows both 

 the external and cerebral surfaces. Externally (fig.l) the part 

 preserved is straight from front to back, with a mesial groove 

 which deepens as it extends anteriorly, so that the two lateral 

 halves of the bone are convex, the anterior groove apparently 

 existing to receive the nasals or premaxillary bone. The 

 outermost lateral parts of the frontal are flattened and directed 

 dowinvard behind, where they widen so as to be inclined 

 to each other at nearly a right angle ; they look ujjward, 

 outward, and slightly forward, rounding into the upper part of 

 the bone. The extreme length of the specimen is 1^ inch. 

 Owing to breakage, its greatest width from side to side is at a 

 quarter of an inch from the hinder termination of the bone, 

 where it measures f inch ; and then it contracts from side to 

 side in a parabolic curve, wliich in passing forward approxi- 

 mates nearer to the u]iper surface of the bone, till the width 

 at the anterior breakage is f inch ; the bone is \^-shaped at 

 the broken end in transverse section. 



The external surface shows two or three impressed lines 

 parallel to the mesial groove. 



Seen from the side (hg. 2), the slightly concave inferior longi- 

 tudinal outline of the bone is nearly parallel with the straight 

 superior longitudmal outline, the de]jth of the bone from above 

 downward in front being more than ^ inch, and the depth behind 

 being y^ inch. The concave lateral outline seen fi-om above 

 (already described) in this view runs diagonally from the 

 front u]iper comer to the back lower comer of the bone. The 

 long triangular posterior part above this line is the lateral 

 region of the frontal already referred to as bent downward. 

 The anterior subtriangular part below the line is concave 

 from back to front, and concave from above doA\Tiward in 

 front, where the two sides of the bone meet at the base so 

 as to form in transverse outline a V-like shape. In the 

 anterior part of this concave area are two small oblong per- 

 forations for vessels. 



Seen from below (fig. 3) , the surface divides into three distinct 

 portions : — (1) the two external concave strips last referred 

 to, which widen and converge in front. Within these there is 

 (2) a long triangular smooth area with slightly concave lateral 

 margins. The area is slightly concave in length, and deeply 

 concave from side to side. Anteriorly there are in it two large 

 ovate perforations for the passage of vessels ; posteriorly the 

 lateral margins are flattened, so that the shai-p lateral boundary 

 is there obliterated. And (3) this median ti-iangular area is 

 excavated behind by two semicircular cavities, making it 

 spear-shaped : the cavities are divided by a median smooth 



