684 



RODENTIA 



Germany is one of the localities mentioned in the text (p. 78), 

 and to a form occurring in Germany the name arwaZ/s was applied 

 by de Selys-Longchamps, the first author to distinguish between 

 this species and agrestis.) 



Diagnosis. — Size small (hind foot, 15 to 17 mm. ; condylobasal 

 length of fully adult skulls, 23 to 25 mm.); colour a nearly 

 uniform, distinctly yellowish brown, the underparts usually 

 suflFused with buffy ; interparietal ligulate in outline, its antero- 

 posterior diameter (exclusive of median spine) not conspicuously 

 more than half transverse diameter. 



Colour. — Upper parts a nearly uniform yellowish brown or 

 brownish bufi", the sides more yellowish than back ; light tips to 

 hairs of underfur usually dull buff, rarely, except in abraded 

 pelage, approaching cream-bufF; black tips to longer hairs not 

 sufficiently contrasted to produce any noticeable effect of " lining " 

 or grizzling. Underparts varying from silvery grey to dull buff", 

 always clouded to a varying degree by the slate-grey under-colour. 

 Feet dull buffy white. Tail bicolor though not conspicuously 

 so, brownish or blackish above, buffy or whitish below. 



Slull and teeth. — The skull of typical Microtus arvalis may 

 best be described as lacking any special peculiarities. It is 

 moderately long and narrow, the brain-case is not particularly 

 deepened, and the dorsal profile is without marked convexity ; 

 interparietal tending to be somewhat ligulate in outline, its 

 antero-posterior diameter in most instances not conspicuously 

 more than half transverse diameter ; nasals sloping forward at an 

 angle of about 23° ; interorbital ridges uniting to form an evident 

 crest in fully adult individuals ; auditory bulla3 rather large, 

 smoothly inflated. Teeth small, the enamel pattern normal, 

 though showing all the phases of individual variation known in 

 the European forms. 



Measurements. — Average and extremes of ten adults from 

 Brunswick, Germany: head and body, 104 (100-111); tail, 40 

 (35-45) ; hind foot, 15*4 (15-16). Two adult males from near 

 base of the Dole, Vaud, Switzerland: head and body, 110 and 

 116 ; tail, — and 36 ; hind foot, 15 '6 and 16. Adult male and 

 female from Fiorentina, Bologna, Italy : head and body, 111 and 

 104; tail, 40 and 32 ; hind foot, 15-8 and 15-6 ; ear, 12 and 12. 

 For cranial measurements see Table, p. 688. 



Specimens examined. — One hundred and seventy-nine, from the following 

 localities : — 



Belgium: Li6ge, 1; Waremme, Li^ge, 6 (U.S.N. M.) ; Maredsous, 

 Namur, 3. 



France : Etupes, Doubs, 21 (B.M., U.S.N.M. and Mottaz) ; Lucinges, 

 Haute-Savoie, 2 ; Montauban, Haute-Savoie, 2 ; Cranves-Sales, Haute- 

 Savoie, 5 ; Scientriers, Haute-Savoie, 2 (Mottaz) ; Poret de Bouconne, 

 Gars, 1. 



Germaity: Brunswick, 16 (U.S.N.M.); Kalbe, Saxony, 1; Schwarzburg, 

 Thiiringen, 2 ; Ummerstadt, Thiiringen, 3 ; Rudolstadt, Thiiringen, 1 ; 

 Kalbe, Saxony, 1 ; Magdeburg, Saxony, 11 ; Moritzburg, Saxony, 5 

 (U.S.N.M.); Dresden, Saxony, 3 (U.S.N.M.) ; Tharandt, Saxony, 1 ; Niesky, 



