18 CETACEA. 



approximate parallelism of the free border of the inner wall with, 

 the inferior border, the descent of the flattened anterior surface to 

 the inferior angle, and the comparatively slight development of the 

 involucrum itself. Specimens of this type of tympanic preserved 

 in the Brussels Museum (Nos. 114, 1637, 1303) are referred to 

 B. primly <enia, an identification which, if correct, woiild necessitate 

 the inclusion of the latter in the present species. 

 Hab. Europe (England and Belgium). 



M. 3512. Cast of the imperfect left tympanic. The original (which 

 is apparently lost) was obtained from the lied Crag of 

 Felixstowe, Suffolk, and is the type of the species ; it is 

 described and figured by Owen in the ' British Fossil 

 Mammals and Birds,' p. 530, fig. 221. Its length is 0,121, 

 and it corresponds very closely with a specimen in the 

 Brussels Museum (No. 1303), which measures 0,120. 



A r o history. 



46682. The imperfect left tympanic ; from Woodbridge. The invo- 

 lucrum is more thickened than in the last specimen. 



Purchased, 1875. 



39011. The imperfect left tympanic ; from the Red Crag of Fclix- 

 stowe. Bowerbank Collection. Purchased, 1805. 



39013. The imperfect right tympanic, in a rolled condition ; from 

 Felixstowe. Bowerbank Collection. Purchased, 1805. 



46681. The imperfect and partially-rolled left tympanic ; from 

 (Fig.) Woodbridge. This specimen (woodcut, fig. 7) is larger 

 than any of the preceding examples, and agrees with a 

 tympanic in the Brussels Museum (No. 114) referred to 

 B. primigenia, which has a length of 0,l-i5 : it has been 

 noticed by the writer in the Quart. Journ. Geol. Soc. 

 vol. xliii. p. 8. Purchased, 1875. 



39010. The imperfect left tympanic, of ratter smaller size ; from 

 Felixstowe. Bowerbank Collection. Purchased, 1805. 



The two following specimens may belong either to this species 

 or to B. primigenia. 



48978. The imperfect left periotic; from Woodbridge. 



Purchased, 1878. 



