16 Merriam — Mammals from Tres Marias Islands. 



Peromyscus madrensis sp. now Tres Marias Mouse. 



Type from Maria Madre Id., Tres Marias Islands, Mexico. No. 89223 

 c? ad. U. S. Nat. Mus., Biological Survey Coll. Collected May 18, 1897, 

 by E. W. Nelson and E. A. Goldman. Orig. No. 11040. 



diameters. — Size rather large ; tail long and scant haired ; ears medium ; 

 color dull pale fulvous; skull without superciliary ridges. In general, 

 similar to P. spicilegus Allen, but much larger, with longer tail and shorter 

 ears. 



Color. — Upper parts pale dull fulvous (almost ochraceous buff] with an 

 indistinct darker dorsal band on posterior half of back ; under parts, lips 

 and feet white ; a salmon or fulvous pectoral spot or streak usually pres- 

 ent; a dark spot on upper side of ankle ; eyelids dark; ears essentially 

 same color as body ; tail dark above and at tip all round ; whitish below. 



Cranial characters. — Skull rather flat and smoothly rounded; rostrum 

 elongate ; no supraorbital ridges. Compared with P. spicilegus, its nearest 

 known ally from the mainland of Mexico, the skull of P. madrensis is 

 larger, the brain case decidedly broader and flatter ; the molar series of 

 teeth actually of the same length (relatively shorter) and somewhat 

 broader. 



Measurements. — Type specimen: Total length 222; tail vertebra? 119; 

 hind foot 26. Average of 12 specimens from type locality : Total length 

 224; tail vertebra 120; hind foot 26. 



Remarks — This mouse, according to Mr. Nelson's notes, is the most com- 

 mon rodent on the islands. He says: " Specimens were taken on all 

 three islands. They were generally distributed in the forest above the 

 shore belt wdiich is infested by land crabs, and were found more com- 

 monly about the fig trees on the high interior ridge of Maria Madre than 

 elsewhere." Specimens from Cleofa Id. are larger than those from Maria 

 Madre Id. (average of 3: total length 229.5 ; tail vertebrae 120; hind foot 

 27.8) and have larger and heavier skulls. Two specimens from Magda- 

 lena Id. have a pale saffron-yellow wash on the belly, probably due to 

 staining. 



Mus rattus Linn. Introduced Rat. 



Mr. Nelson states that this introduced rat, of which he brought back 

 two specimens, was found in small numbers over most parts of Maria 

 Madre Id., where it lives in the forest like the native mice. 



Lepus graysoni Allen. Tres Marias Cottontail. 



Lepus graysoni Allen, Monog. N. Am. Rodentia, 347-348, 1877. Type from 

 Tres Marias Ids., Mexico. 



Mr. Nelson obtained 16 specimens of this very desirable rabbit. He 

 states that the species occurs abundantly on the two larger islands, Maria 

 Madre and Magdalena, and the small San Juanito, and is reported to 

 occur on Maria Cleofa Island also. 



