1 JO 



further illustrated the differences of proportion between them by 

 referring to skeletons of each, and laid before the Committee the 

 following table of comparative measurements : — 



Arv. agreslis. Arv. riparia. 



in. lin. in. lin. 



Length of the head 10§ 9j 



from the first dorsal vertebra to 



the last 10 9 



of the six lumbar vertebrce .... 11| 7^ 



from the first dorsal vertebra to 



the tuberosity of the ischium 2 3 1 9| 



of the os innominatum 7f 6f 



from the sacral vertebrce to the 



end of the tail : 1 9 2 2 



of the scapula 5 4? 



humerus 5 4> 



— i from the olecranon to the carpus 6^ 5\ 



of the femur 6f- S\ 



tibia 7f n\ 



from the os calcis to the end of 



the longest toe 7 • 7| 



It hence appears that the relative dimensions of the body and tail 

 in each of the species are nearly reversed. The number of the cer- 

 vical, dorsal, lumbar, and sacral vertebrce, are the same in both, being 

 7, 13, 6, and 1, respectively ; but the tail of the Jield Campagnol has 

 but 19 vertebrce, while that of the bank Campagnol has 4 more, 

 making 23. The cavity of the thorax is of much larger size in the 

 Jield than in the bank species, the ribs being of greater expanse, and 

 the sternum longer. The head of the bank Campagnol is shorter and 

 more square in its form, exhibiting a greater appearance of strength ; 

 and although it is a smaller animal, with a shorter back as well as 

 shorter limbs, it has actually longer feet than the Jield species. 



Referring to the internal anatomy of the two species, Mr. Yarrell 

 stated, that he had detected no difference in the viscera of the thorax. 

 The stomachs were also of the same form, each presenting an appa- 

 rent contraction at the distance of one-third from the cardiac orifice. 

 The liver of the bank Campagnol was, however, more extensively 

 divided than that of the field species, having seven lobes, while that 

 of the latter presented but five : both are equally destitute of gall- 

 bladder. But the difference in the comparative length of the small 

 and large intestines was most marked : — 



Arv. agreslis. Arv. riparia. 

 inches. inches. 



Length of the small intestines 14| 9£ 



ccecum 2§- 4> 



large intestines 8 10 



These measurements, in which it will be observed that the pro- 

 portions are reversed, appear to indicate some difference in the 

 choice of food, with which Mr. Yarrell stated that he was not yet 



