MR. W. H. PLOWEE ON THE OSTEOLOGY OF THE SPERM-WHALE. 



327 



roughened by numerous concentrically placed ridges. This arrangement is found 

 throughout the whole vertebral column, as far as the epiphyses are separable, on both 

 anterior and posterior surfaces. In the caudal region, the internal thickened area of 

 the epiphysis is more centrally placed, and occupies a larger relative area, its diameter 

 being three-sevenths of that of the whole centrum. 



In a Hyperoodon of about corresponding age, when the epiphysis is removed from 

 the centrum the ridges and grooves of the exposed surface radiate fiom a central point 

 to the circumference, without any such depressed tuberculated area. 



As mentioned before, the entire number of vertebrse is fifty, of which, according to 

 the usual method of division, seven may be reckoned as cervical, eleven dorsal, eight 

 lumbar, and tWenty-four caudal. In this enumeration the vertebra that bears the 

 rudimentary last pair of ribs is counted among the dorsal (although in many characters 

 it approaches one of the lumbar series), and the caudal vertebrae commence with the 

 one that bears at its hinder end the first pair of chevron bones *. Placed in series with 

 their bodies in contact, the vertebrse measure 30' 4", — the seven cervical being 1', the 

 eleven dorsal 6' 8", the eight lumbar 7' 6", the twelve anterior caudal 11' 8", and the 

 twelve posterior caudal 3' 6". 



The following Table gives the weights of all the vertebrae, as well as the length of 

 the body, the greatest width (measured between the extremities of the transverse pro- 

 cesses), and the greatest vertical height (from the summit of the spinous process to the 

 most depending part of the body). Corresponding measurements are given of the 

 vertebrte of the Caithness and the Yorkshire specimen, as far as circumstances would 

 permit : — 



* The arguments in favour of including this vertebra among the caudal series are given in a former paper, 



Description of the skeleton of Inia geoffi-ensix, p. 100, of the present volume. 



J, Z Z 



