. A manual of zoology. Zoology. 550 CHORDATA the pterygoid forniing tlie lamina interna). TIius the hinder sphenoid, Hke the temporal, contains cranial and visceral elements. The vertebra" are conrpletely ossilled and are connected by interver- tebral ligaments, discs of filn'ous cartilage. The cer\ical and rib-bearing thoracic vertebnc are ahvays distinct, and except in the cetacea, lumbar, sacral and caudal vertebne as well. These regions are little variable in extent. The cervicals, including atlas and (epistropheus) number seven except in Bradvpns triihulyliis (q), Cliola-piis l
. A manual of zoology. Zoology. 550 CHORDATA the pterygoid forniing tlie lamina interna). TIius the hinder sphenoid, Hke the temporal, contains cranial and visceral elements. The vertebra" are conrpletely ossilled and are connected by interver- tebral ligaments, discs of filn'ous cartilage. The cer\ical and rib-bearing thoracic vertebnc are ahvays distinct, and except in the cetacea, lumbar, sacral and caudal vertebne as well. These regions are little variable in extent. The cervicals, including atlas and (epistropheus) number seven except in Bradvpns triihulyliis (q), Cliola-piis liofmanni and Manatns (o). In the formation of the sacral region two steps are distinguishable. There is the union of the true sacral vertebra^ with the os ilium and then the fusion of these and with them certain of the caudal vertebra' (pseudo- sacral vertebra') to form the os sacrum. The number of true sacral verteljra is frequently (Marsupials, ungulates, rodents, lemurs) one, as in the amphibia, two (carnivores, pri- mates) or rarely more (EehiJna, many edentates). The pscudosacral verte- bra are rarely lacking entirely; usually their number varies between cme and three. Of the appendicular skeleton the girdles are most interesting. The coracoid, which in monotremes reaches the sternum, is reduced in all other mammals to a small ecraeoid process of the scapula. More rarely the cla\icle is lacking (rapid runners); hi the monotremes it extends to the episternum (fig. 5Q9, CI, Ep)\ else- where it appears to articulate with the sternum, in reality by the intervenlion of interarticular cartilages (once regarded as a rudimentarv episternum, now called preclaviic). In the pelvis all three elemenls are fused to a single OS innoininatiim; puliis and ischium unite ventrallv with each other, enclosing between ihenr the ol'lnralor foramen (lig. ()0()). The pubes of the two sides unite by a symphysis which can extend back to the ischia. The great differentiation of the appendages is also
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectzoology, bookyear1912
