SKELETON OF BIMANA. 



583 



Elements of Human ' temporal bone,' outside 

 view : the confluent ear-capsule, called ' pe- 

 trous portion,' is not here seen. 



bryology nor teleology could have afforded. As the centrum, 5, 

 becomes confluent with 1, a still more complex whole results, 

 which has accordingly been described as a single bone, under the 

 name of ^ os spheno-occipitale ' in some anthropotomies. Such a 

 bone has not few^er than twelve 404 



distinct centres of ossification, 

 correspondiag with as many dis- 

 tinct bones in the cold-blooded 

 animals that depart less from the 

 vertebrate archetype. The spine 

 of the frontal vertebra (frontal 

 bone) is much expanded and 

 bifid, fig. 405, dy d, like the 

 parietal bone ; but the two 

 halves more frequently coalesce 

 into a single bone, with which 

 the parapophysis (postfrontal, b) 

 is connate. Much of the haemal arch is consumed by the rapidly- 

 growing " ossicles of the ear,' and the proper pleurapophysis (tym- 

 panic bone, fig. 404, d) is reduced to the function of supporting 

 the ear-drum, b ; and becomes anchylosed to the squamosal, a, and 

 mastoid, c. The h^mapophysis, fig. 403, 29, hs, is modified to form 

 the dentigerous lower jaw, but articulates, as in other Mammals, 

 with a diverging appendage (squamosal, 27), of the antecedent 

 h^mal arch, now interposed between it and its proper pleur- 

 apophysis ; the two hsemapophyses, originally separate, as in fig. 

 405, become confluent at their distal ends, forming the sym- 

 physis mandibul^e. 



The centrum of the first or nasal vertebra, like that of the last 

 vertebra in Birds, is shaped like a ploughshare, and is called 

 * vomer,' fig. 403, 13 ; the neurapophyses have been subject to 

 similar compression, and are reduced to a pair of vertical plates, 

 which coalesce together, ib. 14, and mth parts of the olfactory 

 capsules (upper and middle turbinals), forming the compound 

 bone called ' ethmoid.' The prefrontals assume this confluence 

 and concealed position even in some fishes — Xij)hias, e. g. — and 

 repeat the character in all Mammalia and in most Birds ; but 

 they become partially exposed in the Ostrich and Batrachia. 

 The spine of the nasal vertebra (nasal bones, ib. is) is usually 

 bifid, like those of the two succeeding segments ; but it is much 

 less expanded. The haimal arch, called ^maxillary,' is formed by 

 the pleurapophyses (palatines, 20) and by the haemapophyses 

 (maxillaries, 21), with which the halves of the bifid haemal spine 

 (premaxillaries, 22) are partly connate, and become completely 



