BALJ^NID^. 17 



lu existing species the whole of the cervical vertebrae are anehy- 

 losed together; but in the fossil forms which have been separated 

 under the above-mentioned names this anchylosis is incomplete ; the 

 centra of all the vertebrae are short. In the tympanic (fig. 6) the 

 superior border of the inner surface is usually nearly straight ; but 

 in one fossil species it may be sinuous. 



33alaena mv^ticttxi^, Linn.^ 



JIab. Arctic Seas. 



38141-2. Two imperfect scajDulae; from a depth of 8 feet below the 

 surface at Deptford. In their large coracoid and acromion 

 these specimens agree with the scapula of the present 

 species ; they are, however, in a comparatively fresh con- 

 dition, and it is highly probable that they were brought 

 to the locality where they were found by human agency. 

 Presented hy the Commissioners of the Metropolitan 

 Board of TFor/.'s, 1864. 



40641. The conjoint cervical vertebrae, in an imperfect condition ; 

 from the banks of the Thames at Limehouse. This 

 specimen (which may not be a true fossil) agrees with the 

 figure given by Van Beneden and Gervais in the ' Osteo- 

 graphie des Cetaces,' pis, iv., v. figs. 5, 6, showing the 

 characteristic contour of the condylar cups of the atlas, 

 the comparatively wide interval between them, and the 

 large size of the nutrient foramen. The remark appended 

 to the last specimen also applies in the present instance. 



Purchased, 1867. 



Balsena afiinis, Owen-. 



Syn, Balcenodon affinis, Owen ^. 



The type tympanic indicates a species closely allied to B. mysti- 

 cetus, and other specimens show that the fossil was fully equal in 

 size to the living form. The tympanic is characterized by its elon- 

 gated form, the comparative straightness of the inferior border, the 

 height of the inner wall at the eustachian part of the aperture, the 

 produced antero-inferior angle, the well-marked keel on the inferior 

 surface (more developed in the young than in the adult), the 



1 Syst. Nat. ed. 12, vol i. p. 105 (17()G). 



2 Proc. Geol. Soc. vol. iv. p. 283 (1843). 



3 Brit. Foss. Mamm. & Birds, tabic facing p. xlvi (1840). 

 TART V. C 



