446 



MURID.E— AGRESTIS 



Notes on tables of dimensions : — The young make occasional excursions 

 from the nursery as soon as they can see, but frequently retain it as 

 their headquarters until they attain sexual maturity, which is not 

 usually until the head and body reaches a length of 90 to 95. 



Specimens with the head and body exceeding no are rare, but 

 probably represent the size regularly reached by really old animals. 

 Occasionally, even larger specimens are captured ; e.g., a male with head 

 and body 123 (Coward, Cheshire). A female nursing young, but not 

 fully grown, sent by the late Lord Lilford from Oundle, Northampton- 

 shire, reached 117 (for further details see my paper in Proc. Zool. Sac, 

 London, 19th May 1896, 599). The status of these "giants" requires 

 investigation. Evidently " voles " continue to grow for a long and some- 

 what indefinite period {cf. above, under Evotomj/s, p. 41 1). 



Skull : — Condylo-basal length, 24-4 to 26 ; breadth : zygomatic, 14 

 to 15-2; inter-orbital, 3-0 to 3-4; occipital, 11 to 12-2; depth, median 

 occipital, 6 to 6-8 ; length : of nasals, 6-6 to 7-4 ; of diastema, 6-8 to 7-8 ; 

 of mandible, 15-2 to 16-2; of maxillary tooth-row, 5-8 to 6-4; of 

 mandibular tooth-row, 5-8 to 6-4. 



Grass Mice ^ are gregarious and sociable animals, restricted 

 under normal circumstances to a diet of green stuflf, preferably 



For an excellent account of the habits of Grass Mice, see Victor Fatio's Les 

 Campagrwles dti Leman. 



