158 FIELD COLUMBIAN MUSEUM ZOOLOGY, VOL. III. 



zygomatic width, 14; interorbital constriction, 4; length of 

 nasals, 9; palatal length from palatal arch to alveolus of incisor, 

 n; postpalatal length, 9; greatest breadth of rostrum, 4; length 

 of mandible, angle to alveolus of incisor, n; height at coronoid 

 process, 7. 



This species belongs to the fraterculus group with long tails, 

 but is very differently colored. The tints are mostly pale except 

 on rump and sides, which have brighter hues. It was only taken 

 by Mr. Heller in one locality, San Antonio, on the western slope 

 of the San Pedro Martir mountains, and seems to have been rare, 

 as only six specimens were secured, three of which had the tails 

 more or less shortened. Its distinctive coloration renders com- 

 parison with other members of the group, save the next species, 

 unnecessary. 



Peromyscus *homochroia. Sp. nov. 



Type locality. San Quentin, Lower California, Mexico. 



Gen. char. Similar in color to P. gait r us, but smaller, tail 

 shorter and black above instead of wood brown; ears compara- 

 tively longer. Skull is shorter in occipito-nasal length; brain 

 case narrower, nasals shorter and more pointed; interorbital 

 constriction greater; pterygoid fossa and palate narrower. 



Color. Above similar to P. gaurus; beneath white with buff 

 patch on chest, between arms; sides ochraceous; hands and feet 

 white; tail above black, with apical third black all round, beneath 

 for remaining part whitish. In some specimens the tail is black 

 all round, in others the whitish hue beneath goes to the tip. 

 Ears brownish black. 



Measurements. Total length, 185; tail vertebrae, 100; hind 

 foot, 20; ear, 21.5. Skull: occipito-nasal length, 24.2; Hensel, 

 18; zygomatic width, 8; interorbital constriction, 3.8; width of 

 brain case, 6.6; length of nasals, 6.5; palatal length, 9; post- 

 palatal length, 8.2; greatest breadth of rostrum, 3; length of 

 mandible, angle to alveolus of incisor, 10; height at coronoid 

 process, 5. 



This in some respects is a diminutive of the previous species, 

 but easily recognizable by its shorter and darker colored tail, 

 and the more or less buff on under parts. The average length 

 of tail is shorter than the measurement given of the type, prob- 

 ably 87 or 90 being the correct number of millimeters. This 

 form is numerous at San Quentin and may be regarded as a 



, similarity of color. 



