MUS. 141 
1. Mus rattus. 7 
Mus rattus, Linneus, Syst. Nat. i. p. 83 (1766, descr. orig.)!; Frantzius, Arch. f. Naturg. xxxv. l, 
p. 2707; Dugés, La Nat. i. p. 188°. 
Hab. Cosmopotitan.—Mexico (Deppe, Mus. Berol.), Guanajuato (Dugés®) ; Costa Rica 
(Frantzius?). 
The Black Rat has been recorded from Mexico, whence a specimen was sent by Deppe 
to the Berlin Museum, and where it was found by Dr. Dugés in the State of Guanajuato®, 
and from Costa Rica, where Dr. v. Frantzius says it is the only true Rat known. Not 
exposed to the competition of the next species, and finding suitable shelter in the 
numerous rents and fissures which earthquakes cause in the clay walls of the houses, the 
Black Rat has become extremely plentiful in most parts of the latter country, although 
it is said to have been first introduced by Spanish ships so recently as the beginning of 
the present century’. 
2. Mus alexandrinus. 
Mus alexandrinus, Et. Geoffroy, Descr. de Egypt, Hist. Nat. i. p. 783, Atlas, pl. v. fig. 1 (1812, 
descr. orig.) *. | 
Mus tectorum, Savi, Nuov. Giorn. de’ Lett., Pte Scient. x. p. 73 (1825, descr. orig.)?; Baird, Mamm. 
N. Am. p. 441°; Rep. U.S. Mex. Bound. Surv. ii. Mamm. p. 42*. 
Hab. Cosmopouitan.—Mexico, Matamoras (Berlandier, U.S. Nat. Mus.*), Nuevo Leon 
(Couch, ib.*), Oaxaca (Sallé, Mus. Brit.). 
This species is very closely allied to the last, with which it is said to interbreed and 
to produce fertile young*. It appears to remain constant in coloration in all climates ; 
and as it especially affects ships, it has become very widely spread over the world. It 
is probably not common, however, in Central America; for the only specimens that I 
know of are the Mexican ones recorded above. 
3. Mus decumanus. 
Mus decumanus, Pallas, Nov. Sp. Glir. p. 91 (1778, descr. orig.)'; Dugés, La Nat. i. p. 1887. 
Hab. Cosmopouitan.—Mexico, Guanajuato, Guadalajara (Dugés?). 
In Costa Rica, as already noticed, the Brown Rat is still unknown; and this is the 
more remarkable, as Dr. v. Frantzius remarks, because it commonly infests the English 
and German ships which visit the port of Puntarenas. 
In Mexico Dr. Dugés observed it in the States of Guanajuato and Guadalajara?; but 
I have never myself seen a specimen from any part of Central America. 
* A, de V'Isle, Ann. des Scient. Nat. 1865, pp. 173-222. Of. Martins, Zool. Gart. 1867, pp. 178-184, 216- 
221 ; Troschel, Arch. f, Naturg. xxxii. 1, p. 170; Giebel, Zeitschr. gesammt. Naturw. 1879, pp. 619-622, pl. ix. 
