172 Field Museum of Natural History — Zoology, Vol. XL 



Skulls of Muridce. (About natural size.) 

 I, Mus musculus; 2, Epimys norvegicus; 3, Peromysctis leucopus; 4, Orysomys paluslris: 5, Neo- 

 toma f. illinoiensis; 6, Evolomys gapperi; 1, Microtus pennsvlvanicus; 8, Fiber zibethicus; 9, Synapto- 

 mys cooperi. 



