MAMMALS OF THE MEXICAN BOUNDARY. 483 



Description. — Size small; coloration pale and cinereous; ear small; 

 mammae, 2 pairs (in one individual, 3 pairs); skull long and narrow. 

 Length, 320 nun; tail vertebrae, L50; hind foot, 34; car, 22. Skull, 

 16 nun by 23.5. The upper coloring is a mixture of ochraceous and 

 cinereous. Below, as usual in desert forms, the white tips to the 

 hairs are much broader than in others. 



h'i murks. The type of this form did not come from the extreme "S. 

 W. corner of Granl Co., New Mexico," a locality that Mr. Anthony, 

 the collector, never visited, hut from a point in the Apache Moun- 

 tains, well to the eastward of the high San Luis range of mountain-, 

 and not far from Monument No. 40, of the Mexican Line. The south- 

 west corner of Grant County is well within the range of true albigula, 

 with the broad Animas plain, and the San Luis, Dog, and Hachita 

 ranges of mountains between it and the type-locality of this animal, 

 which came from the western edge of the Eastern Desert — a very dif- 

 ferent faunal area. A large series of topotvpes of Neotoma inti rmedia 

 angusticeps, from the vicinity of Monument No. 40, Doyle's Well, and 

 Hachita Grande Mountain, furnish several examples that agree closely 

 with the Eastern Desert form, while others of the series are indistin- 

 guishable by cranial or external characters from typical A", albigula 

 from Tucson and Fort Lowell. In other words, the locality is the inter- 

 grading ground of the tw r o forms, and according to usage, it falls to 

 the lot of the first reviewer to decide whether the form angusticeps 

 shall be kept separate from true Neotoma albigula, or be allowed to 

 stand for the desert form to the eastward. I have decided upon the 

 latter course, though there are specimens in our collection taken 50 

 miles farther east that are practically indistinguishable from true albi- 

 gula. In the region around El Paso, Texas, this desert race finds its 

 extreme expression in a small, pale, ash-colored or bufl'v animal. At 

 a camp 50 miles west of the Rio Grande (Monument No. 15), where 

 black obsidian rocks and areas of pale reddish sand were in close prox- 

 imity, dark and pale forms were collected' practically together. One 

 of the darkest had the under surface strongly washed with salmon 

 color, in this respect, being unique in our large series of specimens of 

 the Neotoma albigula group. 



Habits and local distribution. — This wood-rat often builds its. nest 

 among the joints of large prickly-pear cacti, hut it also lives among 

 rocks, and one was trapped in a cavernous hollow under a cliff. At 

 El Paso, it was rather common in rocky situations, and ascended to 

 the summit of the neighboring Franklin Mountains. It was found at 

 every camp thence westward to the Hachita Mountains. I found it 

 at Steins Pass, Lordsburg, and Separ, New Mexico, in April. 1885, 

 Three females taken at Monument No. !•>. March :;i and April :;. 1892, 

 contained 2, 1, and :> fetuses, respectively. 



