I06 MAMMALS OF PENNSYLVANIA AND NEW JERSEY. 



season. This is not always the case. On the brackish tide marshes of Cohan- 

 sey Creek, Cumberland Co., N. J., I found these rat houses tenanted by other 

 inhabitants of the marsh. The meadow mice, least shrews, and marsh rat 

 ( Oryzomys) had their galleries in the base and nests in the top of the house, 

 all three living in one house with the muskrat. The eggs of the snapper and 

 terrapin are also found in these houses, and a large crab's remains were often 

 found. The latter may have been brought there, however, to be eaten by the 

 muskrats. In far northern climates, these houses are built over water of suf- 

 ficient depth to insure against a freezing out. Hearne states that the rats are 

 sometimes frozen in and all perish because of the great size and hardness of 

 the outer dome, which also resists the external attacks of wild animals. 



Description of species. — Our Pa. and N. J. muskrat differs from other nom- 

 inal forms so slightly as to often be indistinguishable from them. It needs 

 no description here, being so different from any other mammal. 



Genus Synaptomys Baird, Mammals of North America, 1857, p. 558. 



Cooper's Lemming. Synaptomys cooperi Baird. 



1857. Synaptomys cooperi Baird, Mammals of N. Amer., p. 558. 



Type locality. — Not known. Type presented by Cooper of Hoboken, 

 N. J. ; probably captured in N. J. or N. Y. near New York City. 



Faunal distribution. — Lower Canadian and transition zones, N. England 

 to Mississippi valley. 



Distribution in Pa. and N. y. — East of the AUeghanies in Pa. I have 

 not found this rare animal except in the upper transition zone and lower 

 edge of the Canadian. One was taken in the Ohio valley (upper austral 

 zone) in Beaver Co., in similar situation to those taken by Quick and Butler 

 in Indiana. In N. J. it is, strictly speaking, confined to the transition zone, 

 becoming modified in the cedar swamps of southern N. J. into the race stonei. 



Habits, description of species, etc. — See next article. 



Specitnens examined. — Pa.: Beaver Co., Beaver, i. Cambria Co., Kings, 

 5 ; Cresson, 3. Clinton Co., Mt. above Round Isl., 7. Monroe Co., near 

 Cresco, i. Sullivan Co., Lake Leigh, i. 



Stone's Lemming. Synaptomys cooperi stonei (Kho2iA?,). 



1893. Synaptomys stonei Rhoads, American Naturalist, vol. 27, p. 53. 



1897. Synaptomys cooperi stonei Rhoads, Proc. Acad. N. Sci., Phila., p. 

 392 ; also ibid., 1897, p. 305. 



Type locality. — May's Landing, Atlantic County, N. Jersey. 



Faunal distribution. — Sphagnum bogs, upper austral zone, eastern border, 

 southern N. J. to Lake Drummond, Va. 



