204 PROCEEDINGS : BOSTON SOCIETY NATURAL HISTORY. 
„ Mus decumanus Pallas. 
Introduced. The brown rat is now abundant throughout eastern 
Georgia, extending south certainly to Jacksonville, Florida. On 
Ossabaw and St. Catherine’s Island it and the roof rat (Mas rattus 
alexandrinus) occurred in about equal numbers and apparently 
interbreed freely. The large series collected on these two islands 
by Mr. Brown contains many specimens that have every appearance 
of being hybrids between the two species. 
Mus rattus rattus Linn6. 
Introduced. The black rat is the least common of the three 
large species of Mus occurring in Georgia and Florida. It appar¬ 
ently not infrequently breeds with the roof rat. At St. Mary’s, 
Georgia, in a little abandoned hut in the woods, I caught a whole 
family of rats, the mother was a black rat, the father a roof rat, and 
of the six young three were black rats and three roof rats. 
« \ 
MUS RATTUS ALEXANDRINUS (Geoff.). 
Mus tectorum Savi, “ Nuovi giornale di lett.” 1825. 
Mus rattus alexandrinus Jerbury and Thomas, Proc. Zool. soc. 
Bond., 1895, p. 553. 
Introduced. The roof rat is the common rat of Georgia and 
Florida and is found over the entire region south to Key West; it 
also occurs on all of the islands. It is most numerous in the settle¬ 
ments and about buildings, although I have trapped it in marshes 
and heavy hummocks, miles from the habitation of man. It appar¬ 
ently interbreeds with M. rattus typicus and M. decumanus , wherever 
it occurs with either of these animals. In places in New England 
where I have found M. rattus typicus and M. decumanus living 
together, they do not interbreed. It is therefore strange that in the 
south M. rattus alexandrinus should apparently cross with both. 1 
*A beaver, probably not Castor canadensis Kuhl., occurs in some parts of western 
Florida and southwestern Georgia. Mr. William Brewster has.trustworthy information 
concerning its occurrence on Chipola Creek, Florida. A thoroughly reliable trapper, 
who formerly lived in southwestern Georgia, has told me that a beaver is still found 
there. I think from all I can learn that beaver do not occur in the region covered by the 
X>resent paper. 
