730 RODENTIA 



antero-external often communicating) and a posterior transverse 

 loop ; each side with three salient and three re-entrant angles ; 

 Wg with the same elements as m.^ but smaller and less well- 

 defined, both first and second pair of triangles tending to open 

 into each other, though the two pairs are normally separated. 



Bemarls. — So far as is at present known Arvicola amphihius 

 is confined to Great Britain. Among the continental species it 

 finds its nearest relative in A. sajjidus of Spain and southern 

 France. Two local races appear to be represented among the 

 specimens examined, though their status is not well defined. 



Arvicola amphibius amphihius Linnauis. 



1758. [Mus] amphibius Linnaeus, Syst. Nat., i, 10th ed., p. 61 (England : 

 based on the Mus major aquaticus of Ray, Quadr., p. 217). 



1816. 7 Arvicola aquatica Leaoh, Syst. Catal. Spec. Indig. Mamm. and 



Birds, Brit. Mus., p. 7 (nomen nudum : " Water Campagnol "). 



1817. Lemmus aquaticus F. Cuvier, Diet, des Sci. Nat., vi, p. 306, part 



(substitute for ampUihius). 

 1812. Arvicola americana Gray, Ann. and Mag. Nat. Hist., x, p. 226 (half- 

 grown individuals supposed to have been taken in South America). 



Co-types in British Museum. 

 1815. ? [Arvicola amphibius'] sub-var. nigricans de S^lys-Longchamps, Atti 



della sesta Riunione degli Scieuziati Italiani, Milano, 1844, p. 322 



(nomen nudum). 

 1857. Arvicola amphibius a. Blasius, Saugethiere Deutschlands, p. 344 



(part). 

 1910. Arvicola amphibius amphibius Miller, Proc. Biol. Soc. Washington, 



sxiii, p. 19, March ^i, 1910. 

 1910. Arvicola amphibius Trouessart, Faune Mamm. d'Europe, p. is. 



Type locality. — England. 



Gcograjjliical distribution. — England and southern Scotland ; 

 exact northern limits of range not known. 



Diagno-iis. — Size maximum for the species (hind foot in 

 adults usually 32 to 35 mm., condylobasal length of skull, 42 mm. 

 or more) ; colour moderately dark, the black rarely in excess of 

 brown on upper parts ; melanism infrenuent. 



Measurements. — Adult male from Diss, Norfolk : head and 

 body, 206 ; tail, 139 ; hind foot, 35. Adult female from Cheadle, 

 Staffordshire: head and body, 185; tail, 118; hind foot, 33. 

 Adult female from Shalford, Surrey : head and body, 201 ; 

 tail, 117; hind foot, 33; ear, 17. Adult male from Garrett 

 Park Lake, Earlsfield, Surrey: head and body, 193; tail, 128; 

 hind foot, 35 ; ear, 16. Adult male from Minster, I. of Thanet, 

 Kent: head and body, 168; tail, 120; hind foot, 32; ear, 18. 

 Adult from Horsham, Sussex : head and body, 186 ; tail, 130 ; 

 hind foot, 33. For cranial measurements see Table, p. 736. 



Specimens cxa mined. Sexcnty -two, from the following localities : — 

 ScoTL.\^'D : Blackwood, Lanarkshire, 3 (Edinburgh) ; Stockbriggs, 

 Lanarkshire, 1 ; Bargsly, Kirkcudbright, 1 ; Stirling, 1. 



