238 
PROFESSOR H. G. SEELEY ON THE STRUCTUtiE, ORGANIZATION, 
The internal border of the orbit is flattened, and is limited externally by a some¬ 
what thickened rounded edge, in the anterior corner of which lies the lachrymal bone. 
It is 4 centims. deep within the orbit, 2 centims. wide on the lateral border in front 
of the perforation for the canal, while the width to the extremity of the narrow 
tongue, which is prolonged superiorly into the narine, is 5 centims. The lachrymal 
perforation is 1'4 centim. long and half as wide, with a depressed rounded border. 
Above the lachrymal bone, and behind the nasal bone, is the pre-frontal bone. It is 
a small ossification above the anterior corner of the orbit, where it projects outward 
in a second sharp but small pyramidal process, similar to the process of the nasal 
bone. The width over these processes is about the same as that across the nasal 
horns. But the pre-frontal bone is no larger than the lachrymal. It measures about 
4 centims. in the vertical direction, and the transverse and antero-posterior measure¬ 
ments are about the same ; so that its small size would suggest that the absence of 
this bone in the skulls of higher Vertebiates is probably a consequence of the frontal 
bone continuing to ossify at its expense. Its largest surface is within the orbital 
border ; and the contour of the orbit causes it to narrow interiorly in the lateral view 
to its junction with the lachrymal bone, above which the transverse spine or horn 
extends. 
The frontal bones are a pair of large flattened horizontal ossifications which extend 
between the orbits, and meet in the median line in a slight ridge, which is only a 
little more elevated than the anterior margin which marks their union with the nasal 
bones, but there is a conspicuous though sipall depression where these bones meet in 
the median line of the skull. Their lateral margins are compressed and convex on 
the under side ; but the lateral contours are concave from back to front, where they 
form the superior borders of the orbits. Posteriorly, the parietal bones are broken 
away, apparently at the suture, and on the right side the post-frontal bone is 
broken away in the line of suture. And these fractures show that the frontal bones 
extend backward in the median line in a broad A shape, which is rather more 
pronounced than the corresponding contour of the nasal bones ; so that each frontal 
approximates to a rhombic form, with the sharp angles outward and forward, and 
made by the pre-frontal bones. The least transverse width between the orbits is 
about 14 centims. The antero-posterior length in the median suture, between the 
frontals, is fully 10 centims. ; the length in the middle of each frontal, from the nasal 
to the post-frontal suture, is 8'5 centims., and on the orbital margin, between the 
post-fi’ontal and pre-frontal, the measurement is about 5 centims., or 9 centims. to the 
deep notch between the pre-frontal and nasal. The length of the post-frontal suture 
on the posterior border is 5’5 centims., where it appears to be separated from the 
anterior end of the parietal by a ridge. The flattened superior surfaces of the frontal 
bones are somewhat concave, owing to the median ridge developed between them 
anteriorly, but where the ridge dies away posteriorly there is a slight transverse 
concavity in the middle parts of the boues. The similar depression in the suture at 
