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In preparing maps showing the geographic distribution of North American microtines, conflicting statements in the literature and identifications that, if accepted, would result in improbable geographic ranges have led to the examination of pertinent specimens with the results given below. The studies here reported upon were aided by a contract between the Office of Naval Research, Department of the Navy, and the University of Kansas (Nr 161-791), by funds provided by the University of Kansas from its Research Appropriation, and by grants for out-of-state field work from the Kansas University Endowment Association.
Grateful acknowledgment is made to persons in charge of the collections at each of the following institutions for permission to use the collections under their charge: Biological Surveys Collection, United States National Museum (herein abbreviated USBS); California Museum of Vertebrate Zoology (MVZ); Chicago Natural History Museum (CNHM); University of Kansas Museum of Natural History (KU); Museum of Comparative Zoology (MCZ); United States National Museum (USNM); Department of Economic Zoology, University of Wisconsin (UWDEZ); and Zoological Museum, University of Wisconsin (UWZM).
Synaptomys cooperi saturatus Bole and Moulthrop
1942. _Synaptomys cooperi saturatus_ Bole and Moulthrop, Sci. Publs. Cleveland Mus. Nat. Hist., 5: 149, September 11, type from Bloomington, McLean County, Illinois.
When Bole and Moulthrop named _Synaptomys cooperi saturatus_, with type locality in Illinois, they, in effect, divided the geographic range of _Synaptomys cooperi stonei_ into two parts (see A. B. Howell, N. Amer. Fauna, 50: 10 (fig. 2), August 5, 1927) since Bole and Moulthrop (_op. cit._) did not assign to any subspecies the specimens from southern Wisconsin that Howell (_op. cit._) had identified as _S. c. stonei_. Bole and Moulthrop's inclusion in their newly named subspecies of a specimen from as far west as East Columbia, Missouri, left in doubt the subspecific identity of specimens from Iowa and a specimen from Arkansas. Howell (_op. cit._) had assigned this material from Iowa and Arkansas to _S. c. gossii_.
Howell recognized that the one individual (168266 USBS) from Lake City, Arkansas, was too young to be identified to subspecies with certainty and assigned the specimen to _S. c. gossii_ "upon geographical grounds" (_op. cit._: 19). Keith R. Kelson and one of us (Hall) compared this specimen with pertinent materials. As a result of this comparison we refer the specimen, on the same grounds employed by Howell, to _Synaptomys cooperi saturatus_.
Specimens from approximately the southern half of Wisconsin (from Kelly Lake southward) were referred to _S. c. stonei_ by Howell (_op. cit._: 16). Now that _S. c. saturatus_ has been recognized, these specimens from southern Wisconsin would be expected to be referable to _S. c. saturatus_. When these specimens were examined and compared (by Hall and Kelson) with other specimens in the United States National Museum the skulls were found to be much larger than in _S. c. cooperi_, smaller than in _S. c. gossii_, and nearly the size of those of _Synaptomys cooperi saturatus_, to which subspecies we refer the specimens in question.
Howell (_op. cit._: 16) referred a specimen from Cassopolis, Michigan, a locality that might be presumed to fall within the range of the more recently named _S. c. saturatus_, to _S. c. stonei_. Bole and Moulthrop did not mention this specimen when they described and named _S. c. saturatus_ (1942). Neither did Burt, but Cassopolis is within the geographic range ascribed to _S. c. cooperi_ on his map (The Mammals of Michigan, Univ. Michigan Press, p. 213, 1946). Examination (by Kelson and Hall) of the specimen (41777 MCZ) reveals that it resembles _S. c. cooperi_ in shortness of hind foot (18 mm.), shortness of tail (18 mm.), narrowness across zygomata (16 mm.), and grayish pelage. In the long braincase, heavy rostrum, greater condylobasilar length, greater lambdoidal breadth, long rostrum, and longer incisive foramina, it agrees closely with specimens of _S. c. saturatus_, to which subspecies we refer the specimen.
Necker and Hatfield (Bull. Chicago Acad. Sci., 6: 54, 1941) referred specimens from Rosiclaire, Illinois, to _S. c. gossii_. These specimens were not mentioned by Bole and Moulthrop (_op. cit._) when they named _S. c. saturatus_ although the specimens presumably would be referred to the newly-named subspecies. We have examined the pertinent specimens (Nos. 15781-15786 and 16049-16054 CNHM) and find that on the basis of dark color, long and slender skull, heavy incisors, and small cheek-teeth, they are referable to _S. c. saturatus_ Bole and Moulthrop. None, however, has a tail so short as the type of _S. c. saturatus_. For that matter, the average length of the tail of six near topotypes (5 mi. W, 2-1/2 mi. S Monticello, Piatt County, Illinois, Nos. 32037-32042 KU) exceeds that of the type (17.4 mm., range 12-20, as compared to 14 mm. for the type).
Synaptomys cooperi gossii (Coues)
1877. _Arvicola (Synaptomys) gossii_ Coues, Monogr. N. Amer. Rodentia, p. 235 (published as a synonym of _Synaptomys cooperi_, but name stated to apply to Kansan specimens of which description and measurements are on p. 236), type from Neosho Falls, Woodson County, Kansas.
1897. _Synaptomys cooperi gossii_, Rhoads, Proc. Acad. Nat. Sci. Philadelphia, 49: 307, June.