PEROMYSCUS. 



SIGMODON. 



Color. Above varying from hair to Prout's brown, mixed with 

 black; dorsal region darkest: lower sides washed with fawn; orbital 

 ring black; under parts white: tail above black, beneath white; feet 

 white: ears blackish. 



Measurements. Total length, 125; tail vertebrae, 48; hind foot, 

 16; ear, 18. 



47. Siginodon. 



I. -': M. 33:= 16. 



Sigmodon. Say & Ord, Journ. Acad. Nat. Scien. Phil., 1825, p. 352. 

 Skull short and wide: length less than twice the zygomatic 

 width: rostrum short, swollen ; superior outline of skull arched ; 

 pointed process of lamellar plate of maxillary nearly dividing the 

 lower part of the anteorbital foramen from the upper; an azygos 

 median process on palatal arch: prominent bead on the supraorbital 

 border extending obliquely backwards to occiput ; audital bullae 

 small. Upper molars three rooted ; front lower molar four rooted \ 

 second and third lower molars three rooted. Sometimes minute 

 accessory fangs are present. Upper molars with two exterior re- 

 entrant folds; the front one has two similar interior folds, the others 

 only one each. Front lower molar has two exterior and three inte- 

 rior reentrant folds; the last two lower molars have generally but one 

 reentrant lobe on each exterior and interior side. Pelage coarse, 

 bristly ; form stout ; tail generally shorter than the body. Ears 

 large; front feet small: hind feet very long: soles naked. 



Fig. 31. Sigmodon hispious. 



.No. 300 Field Columbian Museum Coil. Nat. size. 



Lower tooth row. Upper tooth row. 



Enlarged 4 times. Enlarged 4 times. 



