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Show 1897.] MR. P. E. BEDDARD Otf INTERCENTRA IN BIRDS. 4t)5 5. Note upon Intercentra in the Vertebral Column of Birds. By F R A N K E. B E D D A R D , M.A., F.R.S., Prosector to the Society. [Received April 23, 1897.] The existence of intercentra in the caudal region of the vertebral column has not been much insisted upon. The late Prof. Parker, in the course of some remarks on the intercentra of birds1, observes that they are to be met with in the posterior half of the caudal series in the Cygnet, and in the Cormorant where they are not so numerous. Dr. Gadow, who has said the last published word on this matter, states, in the ' Dictionary of Birds'2, of the caudal vertebras that " they articulate almost entirely by the centrum, which has slightly heterocoelous or concave facets, with the interposition of a fibro-cartilaginous disk, the ventral side of which frequently displays in embryos, but rarely in the adult, a median osseous nodule, the last remnant of the basi-ventral elements commonly called the intercentrum." Prof. T. J. Parker3 refers to two intercentra in the vertebral column of the adult Apteryx in the caudal region, and there are a few scatterd references to the same structures in the writings of Shufeldt4 and others. Thus Prof. Parker6 refers to their existence in Opisthocomus. My experience is directly contrary to that of Dr. Gadow; I find intercentra plentiful in the adult skeletons of many birds, belonging to different groups, in the caudal regionB. It may be useful to state briefly the main facts which the collection of birds at my disposal in the Society's Gardens has enabled me to ascertain. A few previous records of the facts I refer to in footnotes. A few general remarks, which are in effect an abstract of those facts, may perhaps be made first. I use in the following pages the two terms "intercentra" and "hypocentra." By tbe former is to be understood free nodules or pieces of bone lying between the centra and only (at most) articulated with the adjoining centra. By the latter expression the hypophyses, hypapophyses, or haemapophyses of authors, which are apparently downward processes of a given vertebra (apparently, but not really) like those which are so often, particularly among diving birds, found upon the cervical and dorsal vertebras. It is necessary to use two words for these structures, because they are not in every case absolutely the same. ' " O n the Vertebral Chain of Birds," Proc. Eoy. Soc. 1888, p. 474. a Article " Skeleton," p. 856. 3 " Observations on the Anatomy and Development of Apteryx," Phil. Trans. 1891. 4 " Comparative Osteology of Arctic and Subarctic Water-Birds," J. Anat. Phys. 1889, p. 20. 5 " On the Morphology of a Eeptilian Bird, Opisthocomus cristatus" Tr. Z. S. vol. xiii. (1891) p. 63. 6 Marshall, li Beobachtungen iiber den Vogelschwanz," Nederl. Arch. f. Zool. i. p. 194, describes and figures intercentra in the caudal region of the young of - several birds. |