Specimens from the north-central periphery of the geographic range of Z. h. intermedius (northern Minnesota and Wisconsin) on the average are darker, have longer auditory bullae, wider bowed incisive foramina, and (some specimens) a slightly wider pterygoid fossa than is normal in more southern populations. This deviation from the norm is interpreted as intergradation between Z. h. hudsonius and Z. h. intermedius. Individuals from Burnett, Price, and Oconto counties, Wisconsin, and those from Cass and southern Clearwater counties, Minnesota, show such intergradation but are here considered to be Z. h. intermedius.

Specimens examined.—Total, 199, distributed as follows:

Illinois: Coles Co.: Fox Ridge State Park, 1 (UIM). Fulton Co.: 1/2 mi. N Norris, 2 (UIM); 3 mi. N Canton, 1 (UIM); 21/2 mi. N Canton, 2 (UIM); 2 mi. NW Canton, 3 (UIM); 2 mi. W Canton, 1 (UIM); 3 mi. SW Monterey, 1 (UIM). Jo Daviess Co.: near Galen, 3 (FM). Kane Co.: Sugar Grove, 1 (Chic. AS). Lake Co.: Fox Lake, 4 (FM); Pistake Bay, 1 (FM). Perry Co.: 6 mi. S Pinckneyville (near Pyatt), 2 (SITC). Vermilion Co.: Kickapoo State Park, 2 (UIM); Jordan Creek, 3 mi. NE Fairmont, 5 (UIM).

Indiana: Owen Co.: La Fayette, 1 (USNM). Parks Co.: Turkey Run State Park, 2 (1 UM; 1 UIM). Posey Co.: Hovey Lake, 1 (UM); New Harmony, 2 (Clev. MNH); no exact locality, 2 (UM). Sullivan Co.: no exact locality, 1 (UM).

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Iowa: Dickinson Co.: Camp Forester, E Okeboji Lake, 3 (ISC). Emmet Co.: Fort Defiance State Park, 1 (ISC). Hamilton Co.: Little Wall Lake, Jewell, 6 (ISC). Ida Co.: Arthur, 1 (ISC). Lyon Co.: Elgin Township, Sec. 35, 2 (ISC); Riverside Township, Sec. 28, 1 (ISC). Palo Alto Co.: Ruthven, 1 (ISC). Sioux Co.: Ireton, 1 (UM). Story Co.: Ames, 1 (ISC). Winneshiek Co.: Decorah, 3 (UM); Ridgeway, 11 (UM); Conover, 3 (UM).

Kentucky: Lyon Co.: no exact locality, 1 (USNM).

Montana: Dawson Co.: Yellowstone River, 7 mi. NE Glendive, 2000 ft., 1 (MVZ).

Minnesota: Cass County: Cass Lake, 7 (USBS). Clearwater Co.: Itasca Park, Biological Station, 5 (UM). Grant Co.: 3 mi. NW Barrett, 1 (UM). Jackson Co.: 4 mi. E Heron Lake, 1 (UM). Ottertail Co.: 5 mi. NW Vergas, 8 (UM); 4 mi. NW Ashley, 1430 ft., 2. Ramsey Co.: St. Paul, 1 (UM). Sherburne County: Elk River, 23 (2 UM; 6 MVZ; 3 USBS). Winona County: La Crescent, 3 (USBS).

North Dakota: Cass County: Fargo, 1 (USBS). Dickey County: Ludden, 1 (USBS); Ellendale, 1 (USBS). Kidder County: Pettibone, 3 (Chic. AS). La Moure County: La Moure, 1 (USBS). Oliver County: Fort Clark, 3 (USBS). Pembina County: Pembina, 2 (USNM). Ramsey County: Devils Lake, 3 (USBS). Ramson County: Lisbon, 1 (USBS). Richland County: Wahpeton, 2 (USBS); 5 mi. NE Fairmont, Sioux River, 5 (USBS); Blackner, 2 (USBS). Rolette County: Fish Lake, 2 (USBS). Sioux County: Cannon Ball, 4 (USBS). Williams Co.: Grinnell, 2 (USBS).