34 CETACEA. 



anterior extremity of the tympanic is pointed and tlie inner surface 

 more convex than in the last species. 

 Hah. Europe (Belgium and England). 



M. 3533. The imperfect right tympanic ; from the Antwerp Crag. 

 This specimen agrees precisely with the one figured by 

 Yan Eeneden in the ' Ann. Mus. E. Hist. Nat. Belg.' vol. vii. 

 pt. 3, pi. xcvii. figs. 1, 2, and also in form with the 

 tympanic of M. hoops (B.M. No. 1468 c). 



Bi/ exchange with the Royal Brussels Museum of 

 Natural History^ 1886. 



M. 3532. Cast of the slightly imperfect left tympanic of a somewhat 

 older individual. The original was obtained from the 

 Coralline Crag of Suffolk, and is preserved in the Ipswich 

 Museum ; it is described and figured by the present 

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

 pi. ii. figs. 5, 5 a. The specimen closely resembles the 

 one figured by Yan Beneden, op. cit. figs. 9-11, and also 

 an old tympanic of M. hooj)s in the British Museum (No. 2. 

 76. 16. 18). Made in the Museum, 1886. 



Genus BAL-ffiNOPTERA, Lacepede'. 



The skull is small, the nasals are short and rounded, and the interval 

 between the frontal and occipital is comparatively short. The tym- 

 panic (woodcut, fig. 9) is moderately inflated, the inferior aspect 

 forminga comparatively narrow ellipse, which is scarcely wider behind 

 than in front; the inner surface is flattened, without a vertical 

 groove ; the notch for the eustachian canal is deep and sharply 

 defined ; the antero-inferior extremity of the inner surface is pro- 

 duced into a more or less well-marked ridge ; and the outer suiface 

 of the involucrum is flattened ; the inferior surface has two ridges 

 corresponding to those of Megapttra. 



Balsenoptera definita (Owen^). 



Syn. Balcena definita, Owen^. 



Balccnodoa defi'/nita, Owen ^. 

 Bidccnojjttra sihhcddina, Yan Beneden ^. 



1 Hist. Nat. d. C6tac6s, Table d. Ordres &c. p. xxxvi (1804). 



2 Proc. Geol. Soc. vol. iv. p. 283 (1843).— i?atewa. 

 ^ Loc. cit. 



* Bril. Foss. Mamm. and Birds, table facing p. xlvi (1846). 

 « Bull. Ac. E. Belg. ser. 2, vol 1. p. 14 (1880). 



