| Pemberton’s Deermouse is almost certainly extinct. It was large and had a relatively short tail for a deermouse, about equal in length to its head and body. It was one of only two mammals that lived on San Pedro Nolasco Island, a small, arid island in the Gulf of California. The other was - or is - also a deermouse, a subspecies of Peromyscus boylii. Equal numbers of the two deermice were collected in the 1930s, but in recent decades, only P. boylii has been trapped. Chances are the two species competed, and P. boylii won.
Total Length: 210.6 mm +/- 2.0 mm; Tail: 104.9 mm +/- 0.05 mm
Burt, W.H., 1932. Transactions of the San Diego Society of Natural History, 7:176.
Mammal Species of the World