(Subgenus Onychomys, Baird.) 



5. Hesperomys (Onychomys) leucogaster, Maxim. 

 Rare. One specimen secured at Pembina. 



B. Subfamily Arvicolin^. 

 IV. Genus EVOTOMYS, Coues. 



6. Evotomys rutilus, var. gapperi, Coues. 



Observed at various points. This is near its southern limit of 

 distribution in these longitudes. 



V. Genus AKVICOLA, Lacep^de. 

 (Subgenus Myotomes, Rafinesque.) 



7. Arvicola (Myonomes) riparius, Ord. 



Abundant, particularly about the prairie pools. 



(Subgenus Pedomys, Baird.) 



8. Arvioola (Pedomys) austerus, Lee. 



Eastern portions of the Line. Probably represented west- 

 wardly by var. curtahis,"^ Cope. 



VI. Genus SYNAPTOMYS, Baird. 



9. Synaptomys oooperi, Bd. 



Although not observed, the ascertained ranges of this remarka- 

 ble and little known species brings it into the present connection. 

 (Illinois, Kansas, Oregon, Alaska.) 



VII. Genus FIBER, Cuvier. 



10. Fiber zibethicus, Cuv. 



On all the water-courses and permanent pools. 



* The Arvicola imtiperrima. Cooper, Am. Nat. ii., Dec. 1868, p. 535 (Washington 

 Territory), not given in the following pages, is a synonjm of A. austerus, var. curCa- 

 ttis, as I ascertain by examination of the type-specimen. 



