1897.] ME. r, E. BEDDAUD OST HS-TERCENiBA IN BIRDS. 465 



5. Note upon Intercentra in the Vertebral Column of Birds. 

 By Frank E. Beddard, M.A., F.R.S., Prosector to the 



Society. 



[Eeceived April 23, 1897.] 



The existence of intercentra in the caudal region of the bird's 

 vertebral column has not been much insisted upon. The late 

 Prof. Parker, in the course of some remarks on the intercentra of 

 birds \ 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 

 pubHshed word on this matter, states, in the ' Dictionary of Birds ' ^, 

 of the caudal vertebrae 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. Parker ^ 

 refers to two intercentra in the vertebral column of the adult 

 Apteryx in the caudal region, and there are a few scatterd refer- 

 ences to the same structures in the writings of Shufeldt^ and 

 others. Thus Prof. Parker ' refers to their existence in Ojiistho- 

 comus. 



My experience is directly contrary to that of Dr. Gradow ; I find 

 intercentra plentiful in the adult skeletons of many birds, belong- 

 ing to different groups, in the caudal region °. 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 aa abstract of those facts, may 

 perhaps be made first. I use in the following pages the two terms 

 "intercentra" and " hypoceutra." By the former is to be under- 

 stood 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 hsemapophyses 

 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 

 vertebrae. It is necessary to use two words for these structures, 

 because they are not in every case absolutely the same. 



' " On the Vertebral Chain of Birds," Proc. Roy. Soc. 1888, p. 474. 



^ Article " Skeleton," p. 856. 



^ " Observations on the Anatomy and Development of Apteryx," Phil. Trans. 

 1891. 



* " Comparative Osteology of Arctic and Subarctic Water-Birds," J. Anat, 

 Phys. 1889, p. 20. 



^ " On the Morphology of a Eeptilian Bird, Opistkoconms cristafus," Tr. Z. S. 

 vol. xiii. (1891) p. 63. 



^ Marshall, " Beobachtungen uber den Vogelschwanz," Nederl. Arch. f. Zool. i. 

 p. 194, describes and figures intei'centra in the caudal region of the young of 

 several birds. 



