1. Total number of teeth less than 32; maxillary unicuspids less than 5: 2
1'. Total number of teeth 32; 5 maxillary unicuspids: (Sorex) 3
2. Total number of teeth, 28; 3 unicuspids in each maxillary tooth-row: Notiosorex crawfordi.
2'. Total teeth, 30; 4 unicuspids in each maxillary tooth-row: Cryptotis parva.
3.Third and fourth unicuspids approximately equal in size: 4
3'. Third unicuspid obviously smaller than the fourth: 6
4. Each upper unicuspid tooth provided with a pigmented ridge running from apex of tooth lingually to the medial cingulum of tooth, and there ending in a small pigmented cusplet: 5
4'. Each upper unicuspid without lingually directed pigmented ridge or medial cusplet; unicuspids crowded, narrow (from front to back), appearing high-crowned; underparts whitish: 8
5. Condylobasal length greater than 14.7 mm: Sorex cinereus.
5'. Condylobasal length less than or equal to 14.7 mm: Sorex preblei
6. Condylobasal length 20 mm or more; hindfoot fringed with stiff hairs; blackish above, white below: Sorex palustris.
6'. Condylobasal length 18 mm or less; hindfoot without fringe of stiff hairs; grayish or brownish above, tan or gray below: 7
7. Condylobasal length less than 15 mm; total length usually less than 100 mm; hindfoot 11 mm or less: Sorex nanus.
7'. Condylobasal length more than 15 mm; total length more than 100 mm; hindfoot 12 mm or more: Sorex monticolus.
8. Each upper front incisor with a small medial tine: Sorex arizonae.
8'. Upper incisor without medial tines: Sorex merriami.
Key slightly modified from Findley et al. (1975).
Last Update: 27 Jan 2008