496 THE RABBIT CHAP. 



the trigeminal leaves the skull. 1 Between the mastoid portion of the 

 periotic and the posterior border of the tympanic, at the junction of the 

 tubular and bulbous portions of the latter bone, is a small aperture the 

 sty lomastoid foramen^ which transmits the seventh nerve : this and the 

 eighth (VII, VIII) enter the periotic just below the depression for the 

 flocculus of the cerebellum (fl\ A space (IX, X, XI) between the 

 occipital condyle and tympanic bulla gives exit to the ninth and tenth, 

 as well as to the eleventh which is not represented as a distinct nerve 

 in the dogfish and frog ; and the hypoglossal (p. 160), which in 

 Mammals is counted as the twelfth cerebral nerve, passes out through 

 two small apertures (XII) in the exoccipital, just anterior to the condyle. 

 Various other apertures will be noticed in the skull and jaws : through 

 s ome of these branches of certain of the above-mentioned nerves pass, 

 while others transmit blood-vessels. 



The lower jaw or mandible (Fig. 132 A) consists of two 

 halves or rami, each corresponding essentially to the dentary 

 of the frog, which unite with one another in front, at the 

 symphysis, by a rough surface, while behind they diverge 

 like the limbs of the letter V. Each ramus is a vertical plate 

 of bone, broad behind and tapering towards the front, where 

 it bears the incisor teeth : further back, on its upper margin, 

 are the sockets for the cheek-teeth, and behind them is an 

 ascending portion which bears the condyle (cond) for articula- 

 tion with the facet on the squamosal : in front of the condyle 

 is a curved coronoid process (cor). The postero-inferior 

 border, which is rounded and inflected, is known as the 

 angular process (ang.pro). 



The hyoid is a small bone situated at the root of the 

 tongue, anterior to the larynx (Fig. 135, hy\ It consists of 

 a stout body or basi-hyal, a pair of small anterior horns, 

 representing the ventral ends of the hyoid arch of lower 



1 In many Mammals (e.g. dog, cat), the maxillary division of the 

 trigeminal passes out through a separate foramen, behind the 

 sphenoidal fissure ; and the anterior part of the space referred to above 

 is separated off as a distinct foramen for the mandibular division. 



