ZooL.— Vol. III.] HELLER— GALAPAGOS MAMMALS. 235 



probable that James, Duncan, and Albemarle islands, inter- 

 vening between the ranges of the two species of Nesory- 

 zomys, were until recently inhabited by indigenous species 

 of this genus which became extinct upon the introduction 

 of Mus. Oryzomys is doubtless the older genus, and occurs, 

 as a natural consequence, on one of the weather islands, 

 Chatham, from which it has apparently spread to Barrington. 

 The author is under obligation to Mr. R. E. Snodgrass 

 for the measurements of seals in the flesh, to Mr. W. H. 

 Osgood of the U. S. Biological Survey for Waterhouse's 

 account of Mus galapagoensis, and to Mr. A. H. Baldwin 

 for the drawings of skulls. 



Description of Species. 



Family MURID^. 



Mus Linnmus. 



Mus Linnaeus, Syst. Nat. VI, 1766, p. 83. 



Type, Mus rattus Linn. 



Range. — Cosmopolitan. Indigenous in Eurasia and 

 Africa. Galapagos Archipelago (three species of wide 

 distribution). 



Mus rattus LinncRus. 



Mus rattus Linn. Syst. Nat. VI, 1766, p. 83. 



Range. — Cosmopolitan. Indigenous in Asia Minor. 

 Galapagos Archipelago: Albemarle Island (Baur, Hop- 

 kins Expedition), Duncan Island (Baur, Hopkins Expedi- 

 tion), Chatham Island (Hopkins Expedition). 



We may safely assume th.a.t Mus rattus has been an inhabi- 

 tant of the archipelago nearly as long as M. alexandrinus , 

 which was first reported by Darwin on James Island in 1835. 

 On Chatham Island, and at Iguana Cove and Elizabeth 

 Bay, Albemarle Island, Mus rattus is better established than 

 M. alexandrinus. The introduction of M. rattus on Chat- 

 ham Island is perhaps more recent, as it was not observed 

 by Darwin, who collected Oryzotnys galafagoensis there. 



