320 



ME. E. T. NEWTON ON THE CETACEA 



The upper surfaces of the centra are nearly flat from side to side, 

 except at the front, where the median region sinks down into the 

 depression seen between the cups of the atlas. In a side view (fig. 5) 

 the upper surface makes a regular sweep from the hinder part, and is 

 continued upwards towards the top of the atlas. The hinder surface 

 of the seventh centrum is concave and, in outline, flattened from 

 above downwards ; but as it is a little broken both at the top and 

 bottom, the exact form is disguised. The width of this surface, 

 when complete, was probably 10| or 11 inches. 



Measurements. 





Porest-bed 

 fossil. 



1 



BalcBiia BalcBna 



mysUcetus. hiscayensis ? 



Coll. Surg. Brit. Mus. 



2744. 338,/ 



Across both cups of atlas 



Fore and aft length of lower sui-face 

 of centra 



in. 

 17 



9 



in. in. 

 15-5 14 



n-0 i 9 





The cervical vertebrae of Cetacea vary much as to the extent to 

 which they become ankylosed together, and these variations are very 

 characteristic of the difl'erent genera. Among recent Whales the 

 only forms large enough to render a comparison of them with this 

 fossil desirable are BalcEnoptera^ Megajptera. Bahena, and Physeter. 

 In the first of these the cervical vertebrae, as a rule, remain 

 separate; but in exceptional cases two or three may be united. 

 Megaptem generally has two or three of the neck-vertebrae fixed 

 together. BalcEna has aU seven cervical vertebrae soldered into one 

 mass; but the divisions between the bodies are generally, if not 

 always, distinctly seen. In Physeter the first vertebra (atlas) is 

 always free, but the hinder six are more closely united than in any 

 other form. 



The " Forest-bed " fossil has the seven cervical vertebrae closely 

 united, and it is obvious therefore that it comes nearer to 

 Balcena than to any of the other genera mentioned. There are three 

 examples of the united cervical vertebrae of Balcena mystieetus 

 available for comparison in the Museum of the Eoyal College of 

 Surgeons, which, by the courtesy of Prof. C. Stewart, I have been 

 able to examine and measure. In most of their characters these 

 specimens agree with Mr. Backhouse's fossil ; but in none of them 

 are the divisions between the vertebrae so completely obliterated. 

 As regards the number of inferior transverse processes, there is much 

 variation to be observed among them, and even the two sides of a 

 specimen do not always agree. It is evident from this and other 

 differences that a wide allowance must be made for individual varia- 

 tion. The point in which these specimens seem most to diff'er from 

 the fossil is in the concavity of the upper surfaces of the centra. 



