150 GLIRES. 
him for determination by Herr Schneider, of the Natural-History Museum at Basel. In 
addition to its almost hairless particoloured tail and naked soles, it is remarkable in the 
development of the upper edges of the orbits, which are spread into a sort of horizontal 
shelf, instead of rising into perpendicular supraorbital ridges as in Oryzomys. Dr. Peters 
therefore regards it as the type of a separate subgenus, Zylomys; and it will be seen 
that the next species presents the same characters. 
12. Hesperomys panamensis. (Tab. XV. fig. 2.) 
Neomys panamensis, J. E. Gray, Ann. & Mag. Nat. Hist. 4th ser. xii. p. 417, fig. 1, skull (1873, 
descr. orig.) *. 
Hab. Panama (Boucard, Mus. Brit.')—Sovra America, Colombia. 
_ This handsome species was described by the late Dr. Gray from a specimen which 
was obtained by the British Museum from Panama, through M. Boucard. Struck by 
the peculiarities of its skull, Gray made it the type of a new genus, Neomys; but in 
these, as well as in general external characters, it agrees closely with the last species, 
and is consequently referable to Professor Peters’s subgenus Tylomys, of which Neomys 
must be regarded as a synonym. It differs very markedly, however, in coloration, 
though it shares the peculiarity of having a particoloured tail. 
Besides the type specimen, which is now figured, I have seen only one other example 
of this species, a half-grown individual, sent from Medellin to the British Museum. 
3. OCHETODON. 
Reithrodon, Leconte, Proc. Ac. Philad. 1853, p. 413 (nec Waterhouse). 
Ochetodon, Coues, op. cit. 1874, p. 184. 
The North-American Mice with grooved upper incisors were referred by Leconte 
to Waterhouse’s genus Reithrodon; and most later writers have followed his example ; 
but Dr. Coues has shown that they are really quite distinct from that Neotropical 
form, being much more nearly allied to Hesperomys proper. They differ from the 
latter, however, not only in the character already alluded to, but in the first upper 
molar having four roots instead of three (as in Hesperomys), in the inflection of the 
lower edge of the angle of the mandible, and in other minor cranial characters, which 
have been fully described by Dr. Coues in his monograph. 
The two species of Ochetodon which have been found in Central America may be 
thus distinguished :— 
1. O. humilis. Average length about 2"-20, of tail 2”, of hind foot 0""55. Above 
mouse-grey, washed with fulvous on the flanks ; beneath greyish white. 
2. O. mewicanus. Average length 2":92, of tail 5”"72, of hind foot 075. Above 
warm brown, passing into red-brown on the flanks; beneath dirty white. 
