166 GLIRES. 
3. Perognathus fasciatus. 
Perognathus fasciatus, Max. zu Wied, Nov. Act. Ac. Cees. Leop.-Car. xix. 1, p. 369 (1839, descr. 
orig.)'; Baird, Mamm. N. Am. p. 420°; Coues, Proc. Ac. Philad. 1875, p. 283°; Mon. 
N.-Am. Rodent. p. 500°. 
Hab. Norvu America, central regions, from Nebraska southwards+.—Mexico, Chihuahua 
city (Potts, U.S. Nat. Mus.”). 
The naturalists of the United-States Boundary Survey do not appear to have met 
with this, the largest known species of Perognathus; but both Professor Baird? and 
Dr. Coues* have examined specimens from the State of Chihuahua: thence its range 
appears to extend northwards, between the Rocky Mountains and the Mississippi, 
through Texas and Kansas to Nebraska. 
The only observation on the habits of any species of Perognathus with which I am 
acquainted refers to P. fasciatus, and is contained in a brief note by Dr. G. Lincecum, 
who states that it lives in burrows eight to ten inches deep, with subterranean 
galleries and having several outlets *. 
5. HETEROMYS. 
Heteromys, Desmarest, Mammalogie, p. 318 (1820). 
Saccomys, Fréd. Cuvier, Mém. du Mus. x. p. 419 (1823). 
This genus presents us with a combination of the ungrooved incisors of Dipodomys 
and the rooted molars of Perognathus, combined in most of the forms, if not in all, with 
a bristly pelage, in which many of the hairs are developed into fine flattened spines. 
The skull has the temporal region less inflated than is the case in the other genera, and 
is also distinguished by the sharpness of its supraoccipital ridges and the breadth of the 
interparietal. Little has hitherto been recorded of the details of its structure, for which 
we must wait the publication of Dr. Murie’s promised anatomical monograph. 
Of several described species of Heteromys only four appear to me to be well 
established—namely, H. anomalus (Thompson) from Trinidad, H. bicolor (Gray) from 
Venezuela}, and the two following Central-American forms :— 
1. H. desmarestianus. Dull chestnut-brown above, extending to the carpal and 
tarsal joints, tips of spines dark brown; lower parts and feet white. Length 
of head and body about 5-15, of tail 4-75. 
2. H. longicaudatus. Mouse-grey, more or less mixed with tawny, varying in 
extension on limbs, tips of spines black; lower parts and feet white. Length 
of head and body about 5”, of tail from 4°50 to 5°50. 
* ¢ American Naturalist,’ vi. pp. 369, 370. tT Of. supra, p. 165. 
