FELIS SPELtEA. 57 



suture, we get the temporal length of the frontal bone. If this be taken proportionally 

 to the basal length of the skull, it is, so far as our experience goes, invariably greater in 

 tiger than in lion ; the nearest approach to an equality being afforded by a very small 

 tigrine skull in the Oxford Museum, from the Himalayah, and a large Gambian lion (112 ft') 

 in the British Museum. 



The orbital surface may be considered as a section of the interior of a hollow cone, of 

 which the apex is directed obliquely backwards and downwards. The greater projection 

 of the snpra-orbital process causes the concavity to be deeper in lion and Felis spelaa 

 than in tiger. It is pierced near the palatine suture by the small " internal posterior 

 orbital foramen," homologous with that in the human fron to- palatine suture. It serves for 

 the passage of the ethmoidal nerve and artery from the orbit into the anterior end of the 

 cranial cavity, close to the cribriform plate. The postero-external or temporal surface is 

 highly convex vertically, and extends to the temporal ridges and the sagittal crest where 

 the latter reaches the frontals. It roofs in the anterior portion of the cerebral cavity. In 

 old animals of lion and tiger strong ridges are sometimes present in the lower part, 

 directed obliquely upwards and forwards. The mass of solid bone immediately over the 

 anterior lobes of the cerebrum is of great thickness for the size of the animal, being 1'5.5 

 inches in the larger spelsean skull (PI. X), and 154 in a lion in our own possession. The 

 cerebral surface is deeply concave, and excavated for the convolutions of the brain, and for 

 the arteries. A slight groove marks the inter-frontal suture. The vault formed by the 

 cerebral surfaces of the frontals is interrupted anteriorly by an oval arch of about half its 

 height. It leads anteriorly into a chamber, the rhinencephalic fossa, the end of which is 

 closed by the beautiful tracery of the cribriform plate. The abutments of the arch are of 

 great strength. The latter is the equivalent of the "ethmoidal notch" in man. It appears 

 to be generally wider in lion and Felis sjjelaa than in tiger. Its width in the skull 

 figured in PI. X is 055, in a lion's skull of our own 0-54 inch. 



The ethmoidal surface follows for the most part the form of the thin optic plate. The 

 great thickness, however, of the coronal plate makes the roof of the cavity underneath convex 

 longitudinally. The inter-frontal suture is strengthened below by a long spine projecting 

 far into the nasal cavity, and attached to the vertical plate of the ethmoid. It is called the 

 "nasal spine of the frontal," and divides the posterior part of the cavity into two large 

 hollows, which receive the upper and posterior masses of the ethmoidal convolutions. 

 The walls also of the optic plates are ridged longitudinally (see PI. VIII). These 

 cavities for the reception of the ethmoid are called the "ethmoidal sinuses of the 

 frontal." The arrangement of the frontal, cranial, and optic, plates is such as to form 

 opposite the supra- orbital process two large pear-shaped chambers, connected by small 

 orifices with the ethmoidal cavities described above. These chambers are the frontal sinuses, 

 separated from each other by the nasal spine. 



This massive bone affords points of insertion to many important muscles, the largest 

 of which is the great temporal or crotaphite, the antero-external branch of which rises 



