Skull of Rabbit. lOi 



4. The lower jaw consists of a single membrane-bone on 

 each side. 



In other respects the skull of the rabbit does not differ 

 widely in essentials, though, of course, there are numerous 

 differences in detail. The cartilage bones of the cranium are : 

 the four occipitah (b.o, e.g. s.o) ; in front of the basi-occipital 

 is the basi-sphenoid (b.s), above and on either side of which 

 are the ali-sphenoids (a.s) ; in front of the basi-sphenoid is 

 the pre-sphenoid, above which are the orbito-sphe?ioids (o.s) ; in 

 front of this again is the mesefhmoid. The membrane bones 

 of the cranium are the parietals (p) behind, which enclose a 

 small inter-parietal ; in front are the. f rentals (f). 



Of the sense capsules, the auditory consists in the adult of a 

 single periotic bone (p.o), which is formed in the embryo by the 

 ossification of three tracts of cartilage, Has pro-otic, opisthotk, and 

 the epiofic. The membrane bones connected with the auditory 

 capsule are the tympanies (t) surrounding the meatus audi- 

 torius, and the squamosals (s), with which the lower jaw 

 articulates. The optic capsule has no cartilage bone or 

 bones, but the lacrymal (l) may be considered to be the 

 membrane bone connected with it. The olfactory capsules 

 have three complicated and folded cartilage bones, the ethmo- 

 maxillo and naso-turbinals. Of membrane bones connected 

 with the olfactory sense-capsule are the nasals (n) above, and 

 the votner below. 



The first, or mandibular, arch has for its upper piece the 

 malleus, one of a chain of three bones, which pass between the 

 tympanic membrane and the foramen ovale in the periotic 

 bone ; the chain serves to convey the waves of sound impinging 

 upon the tympanum to the internal ear. 



Meckel's cartilage remains unossified in the rabbit, except, 

 perhaps, a small Mento-meckelian element, as in the frog. The 

 palato-quadrate process of the first arch has no cartilage bones 

 developed in it in the rabbit. But the membrane bones, which 

 overlap, or are in connection with this arch, are, firstly the 

 palatines (p.l) and the pterygoids (p.t), which together form the 

 back part of the hard palate : and in front of, and at the outer 

 side of these, the maxillce (m) and premaxillm (p.m), which bear 



