ii6 THE ARTISTIC ANATOMY OF ANIMALS 



an interval, proportionately less extended, however, than 

 that of the human skull. The parietal bone in the ox and the 

 sheep does not enter into the formation of the anterior surface 

 of the skull ; it is formed by an osseous plate, narrow and 

 elongated transversely, which, with the occipital bone, con- 

 stitutes the base of the region of the nape of the neck. It is 

 bent upon itself at the level of its lateral portions so as to 

 occupy the temporal fossa. 



The anterior surface of the frontal bone, which is depressed 

 in the median line in the dog, but plane in the horse, is 

 limited by two crests, which, situated on the prolonga- 

 tion of the parietal crests, diverge more and more from one 

 another in proportion as they occupy a lower position. 

 This surface terminates externally in two processes, which 

 are the homologues of the external orbital processes of the 

 human frontal bone. 



The superior border of these orbital processes, situated 

 on the prolongation of the corresponding parietal crests, 

 contributes to limit the temporal fossa. Each of these 

 orbital processes terminates in the following manner : In the 

 bear, dog, cat, and pig, in which the orbital cavities are in- 

 completely bounded by bone, this process, slightly developed, 

 is not in connection, by its inferior extremity, with an}^ other 

 part of the skeleton of the region. In the ox and the sheep, 

 it articulates with a process of the malar bone. In the 

 horse, it articulates with the zygomatic process of the 

 temporal bone. The inferior margin of this process forms 

 a part of the boundary of the anterior opening of the orbital 

 cavity. 



The supra-orbital foramen, which does not exist in carni- 

 vora, occupies in the horse the base of the orbital process. In 

 the ox, it is situated a little nearer the middle line ; and its 

 anterior orifice opens into an osseous gutter which is directed 

 upwards towards the base of the horn, while inferiorly it 

 meets the inferior border of the frontal bone ; in the sheep this 

 groove is but slightly developed. In this latter, as in the ox, 

 it is the frontal bone which forms the most elevated portion 

 of the skull. In fact, being bent upon itself at a certain level, 

 its external surface is formed of two planes : one, posterior, 



