BALiEXID^. 



31 



which appareutl}^ indicates a very small Whale, somewhat inter- 

 mediate between the smaller fossil species of the present and 

 following subfamilies. 



Palaeocetus sedgwicki, Seeley\ 

 Hah. England. 



41624. Cast of the second, third, and fourth cervical vertebrae. The 

 original, which is preserved in the Woodwardian Museum, 

 Cambridge, was obtained from the Boulder-Clay at Ely, 

 and is regarded by its describer as having been derived 

 from the Kimeridge Clay. The second and third ver- 

 tebrae are anchjloscd, but the centrum of the fourth is 

 free. The original is described and figured by Seeley, op. 

 cit. p. 54, pi. iii. Presented hy Prof, A. Sedgwick. 1869. 



B. BALiENOPTERINE SeCTION. 



There is, at least usually, no anchylosis of the cervical vertebrae, 

 which are thicker than in the Balaeniue section, and the centra of 

 the other vertebrae are more elongated. The tympanic is long, 

 much inflated, rounded, with the involucrum much thickened and 

 more or less distinctly pyriform, and the notch for the eustachian 

 canal always well marked. The tympanic varies in different indi- 

 viduals of the same species much less than in the Ealaenine section. 



The large number of fossil forms described by Van Beneden from 

 the Antwerp CragM'ender the determination of detached vertebra a 

 matter of much uncertainty ; and the close affinity between some of 

 these forms suggests that their distinction may be due to sexual or 

 individual rather than to specific differences. 



Genus MEGAPTERA, Gray \ 



Syn. Megapteropsis, Van Beneden ^. 

 Burtinopsis, Van Beneden *. 



The term Burtinopsis was applied to Balaenopteroids which were 

 regarded as intermediate between Megapiera and Balcenoptcra ; but 



1 Geol. Mag. dpc. 1, vol. ii. p. 54 (1S65V 



2 Zoology of ' Erebus' and ' Terror,' p. 16 (1840). 



3 Bull. Ac. R. Belg. scr. 2, vol. xxxiv. p. 15 (1872). 

 * Ibid. p. 19. 



