. The structure and classification of birds . I Fio. 63.—Lumbar and Sacral Vertebra of an Immature Ostrich(after Mivart).8, 9,10, sacral vertebrae; p, parapophyses ; d, diapophyses. than might be assumed from the last-mentioned differ-ences. The first four caudal vertebrae of Archesopteryx havestrong transverse processes, which are weaker, but present,on the fifth, which thus affords a transition to the remainingsixteen, upon which there are no such processes. In the W. Marshall, Untersuchungen iiber den Vogelschwanz, Ned. i. 1873, p. i94. 114 STRUCTURE AND CLASSIFICATION OF BIRDS
. The structure and classification of birds . I Fio. 63.—Lumbar and Sacral Vertebra of an Immature Ostrich(after Mivart).8, 9,10, sacral vertebrae; p, parapophyses ; d, diapophyses. than might be assumed from the last-mentioned differ-ences. The first four caudal vertebrae of Archesopteryx havestrong transverse processes, which are weaker, but present,on the fifth, which thus affords a transition to the remainingsixteen, upon which there are no such processes. In the W. Marshall, Untersuchungen iiber den Vogelschwanz, Ned. i. 1873, p. i94. 114 STRUCTURE AND CLASSIFICATION OF BIRDS same way the free caudals of carinate birds have transverseprocesses, which are at most faintly represented upon the. fused posterior set of caudals which form the of the posterior caudals of Archaopteryx have fine OSTEOLOGY 116 splints of bone lying on one side, which have been comparedto the ossifications in tendons found among the ptero-dactyles. They may conceivably be misplaced chevronbones. The pygostyle varies much in the degree of its develop-ment. It is weakest in various aquatic birds, such as theauks and grebes, where it is thin and narrow; in morepurely flying birds it is very thick at the base, and is turnedupwards instead of, as in the auks, carrying on the line ofthe tail. In the grebe there is really no more definite aploughshare bone than in the ostrich. The number ofvertebrae which are fused together to form the urostylevaries. In the ostrich Marshall finds four, five in thegrebe and hornbill, six in the duck and in EurylcBmus. The total number of vertebrae in the column variesgreatly; the extremes are something like thirty-nine and sixty-four (reckoning the urostyle
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectbirds, bookyear1898
