35 



Balcenoptem musculus. The right tympanic, from the inner (A) and outer (B) 

 aspects ; recent. ^. (From the ' Proc. Zool. Sue.') 



The tympanic of this species indicates a true Balcenoptera, and is 

 of rather larger size than the corresponding bone of B. goropi, from 

 which it also differs in structure. The Belgian B. sibbaldina (of 

 which the tympanic is undescribed) is almost certainly identical with 

 this form, and is considered to be allied to the existing B. sibbaldi, 

 which attains a length of 80 feet. A fine cervical vertebra from 

 the Red Crag is preserved in the Ipswich Museum. 



Bab. Europe (England and Belgium). 



M. 3521. Cast of the imperfect left tympanic. The original, which 

 is from the Red Crag and is preserved in the Ipswich 

 Museum, is described and figured by the present writer 

 in the 'Quart. Journ. Geol. Soc.' vol. xliii. p. 11, pi. ii. 

 figs. 3, 3 a. It agrees precisely with the imperfect type 

 tympanic figured by Owen in the ' British Fossil Mammals 

 and Birds,' p. 531, fig. 222 (Mus. E. Coll. Surg. No. 2804), 



D2 



