234 FIELD MUSEUM OF NATURAL HISTORY ZOOLOGY, VOL. XL 



The field measurements of six specimens in this Museum, collected 

 by E. Heller at Rosiclare, Hardin Co., Illinois, are as follows: 



The measurements of the smallest and largest of six specimens, 

 which I have examined, from Horseshoe Lake, Missouri, collected by 

 A. H. Howell, in the U. S. Biological Survey collection, are as follows: 

 Total length, 118 and 136 mm.; tail vertebrae, 18 and 21 mm.; 

 hind foot, 18 and 20 mm. 



The distribution of the various forms of Synaptomys is not definitely 

 known. Specimens which I have examined from Indiana, which have 

 been recorded by various authors as cooperi (or stonei, a supposed form 

 which is probably not separable from it), are apparently intermediate 

 between gossii and cooperi, although perhaps averaging nearer the 

 latter, and the same may be said of specimens from east central Illinois 

 (Champaign Co.), while those I have seen from Ann Arbor, Michigan, 

 seem to be intermediate between cooperi and fatuus. Specimens from 

 southern Illinois agree very well with typical gossii, as do those from 

 Iowa; and Hahn states* he secured examples from the Missouri River, 

 South Dakota, which he considered to be gossii, as they differed "mark- 

 edly from the Indiana specimens in being much larger and clumsier, 

 with larger and heavier skull." So far as I know, no specimens of 

 Synaptomys have been taken in northern Illinois or southern Wiscon- 

 sin, but those from northern Wisconsin are apparently fatuus, as they 

 agree in size and cranial characters (including the small narrow incisors) 

 with examples of that form in this Museum from the type locality, 

 Lake Edward, Quebec. Minnesota specimens which I have seen, while 

 not typical, are near fatuus. 



While the eastern form of this Mouse, Synaptomys cooperi, is an 

 inhabitant of swamps and sphagnum bogs, in the western part of its 

 range it does not appear to restrict itself to such localities; in fact, in 

 Indiana, where it appears to intergrade with gossii, by far the greater 

 number have been taken in grassy fields and open woods. Hahn 

 states (/. c., p. 523) that he secured but a single specimen in a swamp, 

 and that they seemed to be confined to areas covered with dense blue 

 grass. In describing the habits of Synaptomys in Indiana, Quick and 

 Butler say: 



* Ann. Rept. Dept. Geol. & Nat. Resources Ind., 1908 (1909), p. 522. 



