1894.] NATURAL SCIENCES OF PHILADELPHIA. 237 



Mr. Nelson states that this species is rather common about the 

 foot of the low cliHs and rocky ledges on the hillsides east of Te- 

 huacau, and that it lives in dense patches of Agave. He says : "It 

 has the habit of making roads about its haunts, very much after the 

 nuuiner of X. alleni. Well-defined trails were found leading along 

 the hillside from rock to rock or to the cover of Agave patches, and 

 betAveen neighboring groups of these plants. Under the shelter of 

 a maguey patch a network of trails could be frequently found by 

 forcing ones way among the spiny leaves. Like A", alleni, these 

 animals did not take grain bait, and were caught by placing traps 

 in their trails. No signs of the nest building habit, so common in 

 the genus Xeotoma, were observed." 



Genus XENOMYS Merriam. 

 (PI. IX, figs. lO-lo; and text lig. 8, e and/, and fig. 4.) 



A't'/iomrs Merriam, Pmc. Biol Soc. Washiugtou, VII, Sept. l.S<)2, 150-103 (Type 

 fr(ini HaeieuiUi Magdaleua, Coliina, ^Mexico). 



Generic characters. — Skull murine; short; audital bulla; greatly 

 enlarged and inflated, broader anteriorly than posteriorly, wheel- 

 shaped, parallel, carotid foramen posterior to middle of bulla and 

 inconspicuous ; squamosal not reaching supraoccipital but ending 

 anterior to plane of auditory meatus, except the slender posterior 

 spicule which reaches over meatus to mastoid ; orbital margins of 

 frontals produced laterally forming projecting supraorbital beads ; 

 lachrymals large ; interparietal large and transversely elongated ; 

 premaxilloe produced anteriorly forming a wing-like extension on 

 each side of anterior nares; angle of mandible short, moderately 

 expanded vertically, inflected; condylar ramus long and high, over- 

 topping coronoid process ; molars large and heavy ; tiaily rooted 

 (upper with three roots each; lower with two roots each); crowns 

 prismatic, made up of broadly rounded alternating salient loops and 

 open re-entrant angles or interspaces; crown of m ;^, shaped in 

 general like letter S but somewhat angular (fig. 4j. 



Externally, Xenomys resembles a sitiall, highly colored wood rat, 

 with rather soft pelage and a large whitish spot over each eye. The 

 tail is nearly as long as the head and body. Nothing is known of 

 the habits of these animals, except that they are nocturual and live 

 in hollow trees. 



Xenomij.i agrees with Hodomys in haviug the mandibular symphysis 

 rather long, straight and u[)turned ; the condylar ramus very long, 



