IJO 



furtlier illustrated the differences of proportion between them by 

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

 following table of comparative measurements : — 



Arv. agreslis, Arv. riparia, 

 in. lin. in. lin. 



Length of the head O 10| O 9l 



froni the first dorsal vertebra to 



the lašt 10 O 9 



of ihe &\'x.\\.\mh&v veiiebrce .... O 11| 7^ 



from the first dorsal vertebra to 



the tuberosity of the ischium 2 3 1 94 



of the os innominatum O 7|- O 6|- 



from the sacral vertebra: to the 



endofthetail 19 2 2 



of the scapula O 5 O 4 



humerus O 5 O 4 



from the olecranon to the carpus O 65 O S5 



of the fer.ncr O 6į O 5| 



tibia O 71 O 7^ 



fron.i the os cnlcis to the end of 



the longest toe O 7 - O 7| 



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

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

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

 7, 13, 6, and 1, respectiveiy ; but the tail of thej?eW Campagnol hsis 

 but 19 vertebrcE, \vhile that of the bank Camjmgnol has 4 more, 

 making 23. The cavity of the t/iorax is of much larger size in the 

 Jlelcl than in the bait/c species, the ribs being of greater expanse, and 

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

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

 and although it is a smaller animal, vvith a shorter back as vveTl as 

 shorter limbs, it has actually longer feet than ihejield species. 



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

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

 The stoniachs were also of the šame form, each presenting an appa- 

 rent contraction at the distance of one-third from the cardiacorifice. 

 The liver of the bank Campagnol, \vas, however, more extensively 

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

 of the latter presented but five : both are equally destitute of galU 

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

 and large intestines was most marked : — 



Arv. agreslis. Arv. riparia. 

 inches. incbes. 



Length of the small intestines 141 9^ 



cceciim 2|- 4 



large intestines 8 10 



These measurements, in which it wiil 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 



