42 CETACEA. 



the present genus, apparently indicates a species agreeing nearly in 

 size with B. borealina. 

 Hob. Australia. 



M. 3506. The hinder part of the much-rolled left tympanic ; from 

 Tertiary (? Miocene) strata at Cheltenham, Victoria. 



Purchased, 1886. 



Genus CETOTHERIUM, Brandt 1 . 



Including : Eucetot/ierium, Brandt 2 . 

 Pksiocetopsis, Brandt 3 . 

 Cetotheriophanes, Brandt 4 . 

 Plesiocetus, Van Beneden 5 . 

 Heterocetus, Van Beneden 8 . 

 Amphicetus, Van Beneden 7 . 



The genus was divided by Brandt into the three subgenera men- 

 tioned above ; the first of which appears to be equivalent to Hetero- 

 cetus s , while the second is the same as Plesiocetus of Van Beneden. 

 Amphicetus is another division which is not of more than subgeneric 

 value. 



The tympanic is much narrower anteriorly than posteriorly, its 

 rough inferior surface forming an isosceles triangle, and the notch 

 for the eustachian canal being smaller and descending nearer to the 

 inferior border of the inner wall than in Balcenoptera. The cranium 

 is longer than in the latter, the interval between the occipital and 

 the frontal being greater, and the nasals more elongated and flattened; 

 the cervical vertebrae are thicker. 



A. Plesiocetine Group. 

 The mandibular condyle has no talon. 



Cetotherium brialmonti (Van Beneden 9 ). 

 Syn. Plesiocetus brialmonti, Van Beneden 10 . 

 This is the largest of the Belgian species, and is somewhat infe- 



Bull. Ac. Imp. St. Petersbourg, vol. i. p. 145 (1843). 



Mem. Ac. Imp. St. Petersbourg, vol. xx. p. 143 ( 1873). 



Ibid. p. 143. 4 Ibid. p. 148. 



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



Ibid. vol. 1. p. 21 (1880). 



Ibid. vol. 1. p. 20 (1880). 



Ibid. vol. 1. p. 21 (1880). 



Ibid. vol. 1. p. 18 (1880). Plesiocetus. 



Loc. cit. 



