468 BULLETIN 56, UNITED STATES NATIONAL MUSEUM. 



the vicinity of the Mexican Line belong to the subgenus Teonoma, " 

 proposed, in 1843, by J. E. Gray for the group of bushy-tailed wood 

 rats. 



KEY TO THE SPECIES AND SUBSPECIES OF HEOTOMA FOUND ON THE MEXICAN BOUNDARY. 



a. Pelage of adult, gray. 



b. Color slatish gray, dark. Length, 390 mm.; tail vertebrse, 180; hind foot, 40; ear, 25; 



skull, 48 by 25 Neotoma microfus (p. 470). 



hh. Color smoke gray, pallid. Length, 310 mm.; tail vertebrse, 125; hind foot, 36; ear, 



22; skull, 43 by 24 Neotoma micropus canescens (p. 471). 



aa. Adult pelage fulvous or ochraceous, not gray. 



c. Anterior loop of first upper molar completely divided by a deep sulcus; nasal and 

 premaxillary bones ending evenly behind. 

 d. Size large. Length, 360 mm.; tail vertebrje, 160; hind foot, 37; ear, 25; 



skull, 47 by 24. Color dark fulvous Neotoma pinetorum (p. 490). 



dd. Size small. Length, 350 mm.; tail vertebrse, 175; hind foot, 35; ear, 20; 

 skull, 44 by 21. Color paler and ochraceous. 

 e. Color pale, ochraceous, slightly darkened by black-tipped hairs; audital 



bullae normal Neotoma mexicana (p. 491). 



ee. Color darker, clay-color, much darkened by black-tipped hairs; audital 



bullae peculiar Neotoma mexicana huBata (p. 491). 



cc. Anterior loop of first upper molar without, or incompletely divided by, a sulcus; 

 nasal bones ending in advance of the premaxillaries posteriorly. 



/. Tail not bicolor; hind feet dusky Neotoma fusdpesmdcroiis (p. 488). 



ff. Tail bicoter; hind feet all white (except the heel in N. attwaien). 



g. Skull of adult more than 45 mm. in length; upper molar series very 

 much broader anteriorly than posteriorly; frontals abruptly expanded 

 behind the interorbital constriction. 

 Ti. Nasal bones enlarged and spatulate anteriorly; hind foot all white 



Neotoma amnulator (p. 472). 

 M. Nasal bones without an anterior spatulate enlargement; hind foot 



with the heel plumbeous Neotoma fioridana attwateri (p. 469). 



gg. Skull of adult 45 mm. or less in length; upper molar series of more 

 nearly equal breadth throughout; frontals never abruptly expanded 

 behind the interorbital construction, but gradually increasing in 

 width from before backward. 

 i. Audital bullae enormously inflated; pelage silky; length, 300; tail 

 vertebra, 125; hind foot, 30; ear, 27. Neotoma desertorum (p. 487). 

 ii. Audital bullae moderately inflated; pelage coarser; size larger, but 

 ears smaller. 

 /. Coloration dark ; skull broad. 

 Ic. Color above, dark olivaceous-gray, lined with blackish 



Neotoma intermedia (p. 484). 

 Iclc. Color above, dark ochraceous-gray. A^cotoma albigtda (p. 476). 

 ij. Coloration pallid; skull narrow. 



a The subgenus Teonoma was revived by Merriam in 1894 and characterized as follows: 

 Tail very large, bushy, and somewhat distichous, like a squirrel's; hind feet very large. 

 Rostrum much elongated, measuring more than one-third the total length of cranium; 

 posterior roots of zygomata widely spreading; sagittal area long, narrow, and sharply angu- 

 lar, its broadest part far back, on or nearly on plane of anterior border of interparietal, 

 whence the sides bend abruptly back to interparietal shields; phenopalatine vacuities closed 

 or open. 



