RODENTIA—MURINAE—NEOTOMA MEXICANA. 49] 
yellowish tinge. The hairs above and on the sides, as well as those on the middle of ‘the belly, 
are plumbeous at base. The tail is dusky above, whitish beneath. 
The skull of this species offers striking points of distinction, from both N. floridana and 
micropus, though most closely resembling the latter. The upper outline of the skull is slightly 
convex, less so than in these other species. The nose is longer than N. micropus, the incisive 
foramina larger ; the zygomata further separated than in N. floridana, but more nearly parallel 
than in NV. micropus. The upper surface of the head is strongly concave, longitudinally, the 
temporal crests well marked. The nasal bones and the slender nasal postero-superior process 
of the intermaxillary end on the same line posteriorly, and do not extend as far backwards as 
the anterior extremity of the orbits, while in the others the intermaxillary processes extend 
considerably backwards of this ; the nasal bones, too, are broader at their middle point than in 
the others. The rami of the lower jaw are higher than in any other species examined; the 
neck of the condyloid process elongated, its axis forming an angle of fully forty-five degrees 
with the base ; the highest point of the condyle is even higher than the coronoid process, instead 
of being considerably below its level. The lower part of the post-coronoid notch is acute, the 
coronoid process smaller than usual; the notch behind the condyloid process is very long. 
When the lower jaw is placed on a horizontal surface, a perpendicular at the posterior extremity 
will be tangent to this and the posterior extremity of the condyle, instead of falling consider- 
ably in advance of it as in other species. The body of the bone in advance of the molars is 
less deep than usual. The lower molars are narrow and quite parallel, the lobes narrower, and 
their sides more parallel. 
I do not feel sure, however, that all these peculiarities of the skull will be found characteristic 
of the species, as individual specimens sometimes vary considerably. 
| 565? 
| 289. 
General dimensions. l 
Inches. | Lines. || Inches. | Lines. 
as | 
INORG LO OCOD Ul s 5 arn ac ea enews ne eee t aoa aoe \eeceeses |HEeoee ee 94 
CREE ae ee ae setae ee ae os ae on a aa ae | | 1 8 
RODE OMtAll Sones ease ee eo ee eee eae 7 3 Se Vi eae 
Tail, from root to end of vertebrae -.- -..---------. Lost Lost | 5 e+ ----- 
LP oe oes tee ee ae See eel eee | 3 
Bard help iu NOstenionly =a. Saas see ee ae as soe loam on = Wo petessee jeseecoee 
BN ECTIOU i= olen Son ta epee = peSeesss| tie | Es See 
internally above notch ---------------- |-n------ 103” |/Essaes- 3 We as 
Axm, fore foot to end’ of claws...<-=-22-4ss-s25e2--- elo ee 7 eee eee 7 
longest) claw=+ >32 {soe 222256. sete se [eect == re cee 
Leg, hind foot, from heel to end of claws ------------ 1 2 | 1 2 
TOTIRGR in CLAN Se ett a eee ar a oe ee teas ot red wie ||~ mie |-------- 
tociand: claw s2= 5.22555 =- 6 asa ca toe See Shy asee= = 4 
The specimen collected by Dr. Webb was captured in October, 1852, at Chevate, near Ojo 
Caliente, on the road between El Paso and Chihuahua, about one hundred miles from the latter 
place. Their curious structures were seen in various directions between the rocks, and consisted 
