274 Rev. L. Jenyns on some of 



the A. arvalis, it may be useful just to place side by side the 

 essential differences between these two species, which after 

 all are not very great, and on the true value of which I do not 

 pretend to speak positively. 



A. arvalis. — Body 4 inches : ears projecting out of the fur : 

 colour of the fur above reddish brown ; beneath greyish 

 white, the hair sometimes dusky at the roots. 

 A. neg-lecta. — Body 5 or b\ inches : fur long, entirely con- 

 cealing the ears : colour of the fur above reddish brown, 

 beneath whitish, with a large portion of the hair from the 

 root upwards dusky. 

 To these differences may be added the absence of a gall- 

 bladder in the A. arvalis, and its presence in the A. neglecta, 

 if further observation prove the constancy of this character ; 

 also the differences in the cranium above pointed out. 



(13.) ArvAcola rubidus, De Selys? {A. 7'iparia, Yarr.) — I 

 cannot but feel some doubts as to the identity of the A. ri- 

 paria of Mr. Yarrell and the A. rubidus of De Selys, notwith- 

 standing the opinion of this last author, from the striking dif- 

 ference observable in the cranium of our English specimens, 

 as compared with the figure and description of this part in 

 the A. rubidus, given in the * Micromammalogie.' M. de 

 Selys says of this last, ^' crane ])lus allonge que chez lesautresi'^ 

 and again, "orbites moyens, allonges, 4troits en arrih'e, les ar- 

 cades zygomatiques etant pen arquees." His figure is accord- 

 ing to this description, and represents the length of the cra- 

 nium as rather more than twice its breadth across the zygomatic 

 ai'ches. But neither will agree with a cranium in my posses- 

 sion, which is not more elongated than that of the A. neglecta, 

 spoken of above, and in which the orbits are as broad, and 

 the zygomatic arches as much bent, as in that species, the 

 breadth across being considerably more than half the entire 

 length. This cranium belongs to an Arvicola, which was ob- 

 tained by Mr. Thompson from Aberarder, where it was taken 

 in company with the A. neglecta, and along with which it was 

 kindly forwarded to me in 1839. Neither he nor myself had 

 any doubts of its being the A. riparia of Yarrell, though in 

 size it rather exceeded any specimens I had seen previously. 

 The following were its measurements : — 



in. lin. 



Head and body 3 9 



Head 1 Oh 



Tail 2 



Ears 4i 



Hind-foot 8 



Fore-foot 4^ 



