142 GLIRES. 
4, Mus musculus. 
Mus musculus, Linneus, Syst. Nat. i. p. 83 (1766, descr. orig.)’; Tomes, P. Z.S. 1861, p. 281°; 
Frantzius, Arch. f. Naturg. xxxv. 1, p. 271°; Dugés, La Nat. i. p. 138°. 
Hab. Cosmopouttan.—Mexico (Sallé, Mus. Brit.), Guanajuato, Guadalajara (Dugés*) ; 
GuaTEMALA, Duefias (Salvin, Mus. Brit.?) ; Costa Rica (Frantzius®). 
As in every other part of the world settled by Europeans, the House-Mouse appears 
to be abundant throughout Central America. Mr. Tomes observed of two specimens 
sent by Mr. Salvin from Guatemala that they were smaller than European examples, and 
that he had noticed the same difference in others sent by Fraser from Colombia’. 
Dr. v. Frantzius remarks that in Costa Rica Mice may be seen running about the floors 
of the best houses in broad daylight, and that, as they do little damage compared with 
Rats, no trouble is taken to extirpate them®. 
2. HESPEROMYS. 
Hesperomys, Waterhouse, Zool. Voy. ‘ Beagle,’ i. p. 75 (1839). 
The greater number of the Muride of the New World are referable to Mr. Water- 
house’s genus Hesperomys, as restricted by Professor Spencer F. Baird * and Dr. Elliott 
Couesf. ‘The members of this extensive genus all agree in having a typically murine 
skull, and in their dentition—the incisors not being grooved, the first having three roots, 
and the second and third diminishing in size successively. They differ, however, among 
themselves in many other important characters, and form a number of separate groups, 
some of which might well be regarded as of generic value, were it not for the inter- 
grading forms which connect one with another and prevent their being sharply defined. 
Nevertheless they may be conveniently retained as subgenera, the recognition and defi- 
nition of the numerous species being thereby rendered more easy. Of these subgenera 
Dr. Coues recognized six North-American forms, to which I think at least two more 
(Nyctomys and Tylomys) must be added, making eight in all. Of these, four are repre- 
sented in Central America by about twelve species. These may be thus characterized:— 
A. VEspERoMYs, Coues, Proc. Ac. Philad. 1874, p.178. Form mouse-like; ears 
large, scantily haired; tail moderate or long, closely haired; small internal 
cheek-pouches usually (or always?) present. Skull with no marked supra- 
orbital process. 
1. H. teguinat. Above warm dark reddish-brown, passing into deep fawn below. 
Length of head and body 3"-25, of tail about 2”. 
* Mamm. N. Am. p. 458. 
t Proc. Ac. Philad. 1874, p. 178; Mon. N.-Am. Rodent. p. 43. 
t This species is only provisionally placed here. Of. infra, p. 144. 
