Kansas, including one topotype), S. c. relictus differs in: Dorsal coloration, in comparable pelages, darker, venter lacking buffy tinge; skull averaging larger in all cranial dimensions (except rostral length, which is approximately the same), especially breadth of upper incisors and length of molariform tooth-rows; nasals broader anteriorly; auditory bullae nearly equal in size, thus relatively smaller. From Synaptomys cooperi paludis (holotype and paratypes) of Meade County, Kansas, S. c. relictus differs in: Skull averaging smaller in all cranial measurements except rostral length and breadth of upper incisors, which are approximately the same, and breadth of nasals, length of incisive foramina and length of molariform tooth-rows, which measure more; nasals relatively (48 per cent of length of nasals) as well as actually broader anteriorly; anterior border of zygomatic plate more concave; auditory bullae smaller; infraorbital foramina larger when viewed anterolaterally. S. c. relictus closely resembles S. c. paludis in color and external proportions.

Remarks.—The total population of Synaptomys cooperi relictus may be small because the only suitable habitat known to me for these mice is the dense, grassy area, approximately 100 yards wide and one mile long, around some of the rearing ponds and along the creek at Rock Creek Hatchery. It has been taken there in association with Cryptotis parva parva, Blarina brevicauda carolinensis, Reithrodontomys megalotis dychei, Peromyscus maniculatus nebrascensis, Microtus ochrogaster haydenii, and another relic, Microtus pennsylvanicus finitis. All specimens of the newly named bog lemming are from the border zone between the wet-substrate habitat of M. p. finitis and the drier habitat occupied by M. o. haydenii. Approximately 3000 trap nights produced the four known specimens.

S. c. relictus, like S. c. paludis, represents a relict population of the more southwesterly distribution of the subgenus Synaptomys during Wisconsin and post-Wisconsin times. Additional relict populations likely will be found in the eastern Great Plains.

The new subspecies is intermediate in some features between paludis and gossii. The type locality is separated from that of paludis (14 mi. SW Meade, Meade County, Kansas) by a distance of approximately 220 miles over habitats largely unsuitable for bog lemmings. The nearest locality of record for S. c. gossii to the east of the type locality of relictus is at Hunter, Mitchell County, Kansas (see Cockrum, Univ. Kansas Publ., Mus. Nat. Hist., 7:196, 1952), approximately 200 miles distant. The locality of record of gossii in Nebraska nearest to the type locality of relictus is even farther eastward—1 mi. N Pleasant Dale, Seward County (KU 50188).

Specimens examined.—Four, from the type locality (KU 51617, 72601-03).

Transmitted March 11, 1958.