328 MR. W. K. PARKER ON THE OSTEOLOGY OF BAL^NICEPS REX. 



cellularity of the bone, and these lower vertebrae gradually increase in width ; so that 

 the seventeenth is more than IJ inch across the diapophyses, the ninth being only I^ 

 wide at the same part. In the two last cervicals the upper articular surface for the 

 ' tubercle ' of the rib is flat, that for the round smooth ' head ' is rather deeply concave, 

 as in the dorsal vertebrae. 



The formation of the carotid ' haemal ' canal in the neck of birds is exceedingly inter- 

 esting, but its anatomy is not a little obscure. In 1844 Professor Owen' taught that 

 these were typical vertebrae ; but this mistake was soon corrected by him, and the true 

 nature of these canals as productions of the centrum (in a part of the body of the bird 

 where there are only very small rudiments of ribs and no haRmapophyses or haemal 

 spines) was shown. To the writer's mind, the distinction between parapophyses and 

 hypapophyses is faulty, dividing as it does parts that are essentially one in signification. 

 In his masterly memoir the ' Croonian Lecture',' Professor Hu.xley has shown the great 

 uniformity and simplicity of the structure of the vertebral column in all the Vertebrata, 

 and to his views our own have for a long time been approximating. But many a passage 

 from Professor Owen's most invaluable works might be brought to show that these struc- 

 tures are far more simple and uniform than would appear from their nomenclature. 



In Professor Owen's Report ' On the Archetype and Homologies,' read at the Meet- 

 ing of the British Association held at Southampton in 1846, we have the following 

 remarks (page 254 of the General Report) : — 



"In the Sturgeons {Sturio, Polyodon) the inner layer of the fibrous capsule of the 

 gelatinous notochord has increased in thickness, and assumed the texture of tough 

 hyaline cartilage. In the outer layer are developed distinct, firm, and opake cartilages, 

 the neurapophyses, which consist of two superimposed pieces on each side, the basal 

 portion bounding the neural canal, the apical portion, the parallel canal filled by fibrous 

 elastic ligament and adipose tissue ; above this is the single cartilaginous neural spine. 

 The parapophyses are now distinctly developed, and joined together by a continuous 

 expanded base, forming an inverted arch beneath the notochord for the vascular trunks, 

 even in the abdomen. Pleurapophyses are articulated by ligament to the ends of the 

 laterally projecting parapophyses in the first twelve or twenty abdominal vertebrae ; in 

 the anterior ones those ' vertebral ribs ' are composed of two or three distinct cartilages. 

 The posterior pleurapophyses are short and simple. The parapophyses gradually bend 

 down to form haemal arches in the tail, at the end of which we find haemal cartilaginous 

 spines corresponding to the neural spines above." And again in page 25.5 : — " In the 

 osseous fishes I find that the centrum is usually ossified from six points, four of which 

 commence, as Rathke describes, in the bases of the two neurapophyses and the two 

 parapophyses; but the terminal concave plates of the centrum are separately ossified ^ 

 They coalesce with the intermediate part of the centrum, which is sometimes completely 



' See his Lectures on Comp. Anat., vol. ii. p. 44. ' Delivered at the Ro^al Society, June 17, 1858. 



2 Vogt, Williamson, and Huxley speak of this annular ' diapophysis ' as being ossified from only one centre. 



