In the skeleton of the adult male Balmna Mysticetus, which is 

 41 1 feet long, figured by Esehrieht and Eeinhardt (t. 2), the head 

 occupies two-fifths of the entire length of the skeleton. In the new- 

 born specimen figured on the first plate of their interesting essay, the 

 body is much longer, and the head only occupies about two-sevenths 

 of the entire length, showing that the head increases in length at a 

 greater rate than the body. This seems general in whales : for the 

 skuU of the foetal Eubalcena australis, figured by Professor Huxley 

 in his ' Elements of Comparative Anatomy ' (fig. 107, on p. 270), is 

 short and broad for the genus ; the skull of the foetal and young 

 Balcenoptera rostrata, figured by Esehrieht, is shorter than the adult 

 skull ; and that of the foetus is very short indeed. 



The frontal bones of the skuU of the foetal or new-born specimen 

 are broader and shorter than in the adult, as may be observed in the 

 figures of Cuvier, Esehrieht, and Huxley. 



I. Atlas united with the other cervical vertebree into one mass. 



A. Head very large ; of adult, two-fifihs the entire length. Baleen elongate, 

 slender, with a single series of veryjme elongate central fibres, forming 

 a Jme flaccid fringe. Enamel thick, polished. 



1. -RAJaMSK. 



The first rib like the others, single-headed. The tympanic bone 

 rhombic; aperture oblong, only slightly contracted at the upper 

 end, and about two-thirds the length of the bone. 



Balsena, Gray, Proc. Zool. Soc. 1864, 201 ; Ann. ^ Mag. Nat. Hist. 

 1864, xiv. 348. 



Fig. 1. 



BaliBna Mysticetus. Cuv. Oss. Foss. v. t. 25. f. 10. 



Head about two-thirds of the entire length, rather blunt, swollen, 

 with a slight beard consisting of a few scattered white hairs on the 

 anterior extremity of both jaws (Scoresby, Arctic Eegions, i. 458). 



Skull high and contracted behind ; the frontal very narrow, mar- 

 ,ginal, directed backwards; tympanic bone, rhombic, large, aper- 



