570 



PHOCA VITULINA HARBOR SEAL. 



to the small size of these vertebrae, but in part to their reduced 

 number.* 



Measurements of the principal parts of the skeleton in Phoca vitulina, Phoca green- 

 landica, and Phoca fasticta. 



* The vertebral formulae of the five species of northern Phocids, of which 

 I have before me several complete skeletons of each, are as follows : 



The number of sacral and caudal vertebrae, especially the latter, may be 

 subject to individual variation, as Gerrard (Cat. Bones of Mam. in Brit. 

 Mus., 1862, p. 143) gives 3 sacral and 12 caudal for P. mtulina. Lilljeborg 

 also gives only 3, but adds that a very old skeleton has 4. In each of the 

 four skeletons of this species which I have examined 4 vertebrae are firmly 

 anchylosedto form the sacrum; in three of these the caudal series is imper- 

 fect. Gerrard gives also only 3 sacral for Erignathus barbatus (Ibid., p. 145), 

 while in two skeletons I find 4 in each. 



Lilljeborg gives the length of the tail in Phoca mtulina at 69 mm. and in 

 Phoca f oetida, male, 150 mm., female, 144. 



tin two very old skeletons of Phoca grcenlandica I find the sacrum to con- 

 sist of only three anchylosed vertebra. In both the other species the sa- 

 crum consists of four anchylosed vertebrae. 



