^OPEJ PALEONTOLOGY MIOCENE PERIOD. 481 



a stout horn-core, which is principally composed of a production of the 

 nasal bone. The distance to which these supporting elements rise dif- 

 fers in the species. The horn-cores are a striking feature of the genus, 

 and var.v in shape and proportions in the species. In one, they areru- 

 dimental ; in others, short and stout; in another, long, slender, and curved. 

 The nature of their investing membrane remains unknown, but the ex- 

 tremities in several of them {S. acer, 8. hucco) are so rugose with 

 coarse exostoses as to suggest strongly a cartilaginous or corneous 

 .appendage or continuation representing the deciduous horn of the deer. 

 The nasal bones are co-ossified in most of the species, and present vari- 

 ous forms in the different species. In all the specimens, the sutures on 

 the upper face of the skull are obliterated, so that it is difficult to deter- 

 mine the true structure. The orbits being far anterior and but little 

 behind the line of the bases of the horn-cores, it is evident that tlie 

 frontal bones are produced well forward. The nasals are, however, pro- 

 duced broadly between the anterior portions of the frontals. 



The hasioceipital and basispheuoid are narrowed and bounded by a 

 large con&nent foramen lacerum anterms etposterius. The petrous bone 

 is small and deeply set. There is a transverse paramastoid process, 

 and a very large transverse postglenoid process. The mastoid process 

 is thickened and recurved so as to be nearly in contact with the post- 

 glenoid, and to inclose the external auricular meatus. The side-walls 

 of the posterior nasal meatus are prolonged, and form an abrupt obtuse 

 angle posteriorly where the border rises to the basispheuoid. The pyra- 

 midal iDrocess of the palatine, the pterygoid, and the pterygoid ala of 

 thjB sphenoid, which compose each, are closely co-ossified. The external 

 side of this plate is deeply longitudinally grooved, which terminates 

 posteriorly in a foramen, the spheno-orbital. The posterior base of the 

 plate is longitudinally i)erforated, and in line with this short tube is a 

 large foramen opposite the glenoid cavity. The forumen ovale is prob- 

 ably confluent with the/, laceruni anterius as in Eohasileus and Rhino-, 

 cerus. The palate is incised to the front of the last molar. In outline, 

 it is quite narrow when compared with the large molars^ the diameters 

 of the two being about equal. 



The mandible is small when compared with the cranium, and contracts 

 rapidly forward. The condyle is large and transverse, and the coronoid 

 process small, narrow, and close to the condyle. The angular region is 

 strongly convex both backward and downward. The inferior margin 

 of the ramus is without tuberosities, and the symphysis co-ossified, 

 shallow, and oblique. 



The cranial cliamber is elongate, and is divided into three departments 

 for corresi3onding segments of the brain. The posterior is elongate- 

 oval, for the reception of the cerebellum. It is separated from the 

 median division by a thin tentorium, whose union with the superior 

 walls indicates that the cerebral hemispheres did not overhang the cere- 

 bellum. The anterior border of the hemispheres is indicated by a 

 thickened, arch-like contraction of the lateral and superior cranial walls 

 within, and is situated much behind the orbits, as in perissodactyles 

 and some carnivora. This chamber is divided longitudinally by a thin 

 falx, and each iDosterior lobe is again divided vertically by a thin osseous 

 septum, thus accommodating two convolutions. The external of these 

 is supported underneath by a thin septum from the outer wall. The 

 falx divides or forks at its anterior extremity into two vertical laminae, 

 which continue parallel to each other to the inner bases of the nasal 

 horns. They are here continuous with the external wall, forming the 

 posterior boundary of the anterior narial opening. They form the 



31 G s 



