RODENTIA-MURINAE-MUS TECTORUM. 
441 
MUS TECTORUM, Savi. 
White Bellied Rat; Roof Rat. 
Mus tectorum, Savi, “Nuovi Giornale di Lett. 1825.” 
Bonaparte, Fauna Italica ; plate. 
Keys. & Blasius, Europ. Wirb. 1842, 36. 
Wagner, Suppl. Schreb. Ill, 1843, 405. 
Burmeister, Thiere Brasiliens, I, 1854, 154. 
Giebel, Zoologie, 1855, 555. 
Mus alexandrinus, “Geoffr. Desc. de l’Egypte.” 
Mus flaviventris, “ Licht. Brants Muizen, 108.” 
Mus in/uscatus, “Wagner, Suppl. Schreb. Ill, 1843, 445. 
Mus setosus] “Lund, Bras. Dyr.” 
? Mus railus, var. Aud. & Bach. N. Am. Quad. I, 1849, 191, 194 ; plate xxiii. (Light-colored figures.) 
Mus americanus, “ Seba, Thes. II, 30 ; tab. xxix.” 
Erxleben, Syst. An. I, 1776, 385. 
Leconte, Pr. A. N. Sc. Phil. YI, 1853, 414. 
Rat d’Amerique, “Brisson, Reg. An. I, 172.” 
Sp. Ch.—S maller than the Norway rat; tail from one to two inches longer than head and body, sparsely hairy, with about 
240 annulations; color above, like the Norway rat; beneath with upper surface of feet, pure yellowish white. Like the 
Norway rat, the fur of the back is coarse, and mixed with longer stiffer bristly hairs. 
This rat, in general appearance, exhibits a close resemblance to Mus decumanus, but may 
be readily distinguished by appreciable characters hereafter to be pointed out. The head of 
this species is compressed, and rather blunt. The eyes are pretty large, but smaller than in 
Neotoma. The whiskers are long, black, arranged in five series. The upper lip is cleft to the 
base of the incisors, whence to the end of the snout, a distance of about a quarter of an inch, 
it is indented by a furrow which passes along the septum, and the bottom and sides of which 
are free from hairs. The hairs come to the extreme end of the muzzle above, so that no naked 
portion is visible from above ; the edge of the hairy upper surface is separated by a transverse 
constriction from the septum, and below it is another transverse furrow which, with the longi¬ 
tudinal one already described, divides this septal portion into four spaces. The nostrils are 
terminal, but situated slightly oblique. 
The ears appear very large, exceeding considerably those of M. decumanus, and almost like 
Neoloma . They are, however, of thicker membrane and entirely destitute of an antitragal 
valve ; they are sub-orbicular, rather higher than wide, and very scantily and sparsely covered 
with short hairs, so as to appear almost naked on both surfaces. 
The thumb of the fore finger is very rudimentary, with a broad flat nail; there are five large 
tubercles on the palm ; the two posterior very large. The hind feet are short and broad ; the 
soles entirely and conspicuously naked, even to a short distance behind the heel; there are six 
tubercles on the sole ; two at the bases of the three middle toes, and one each at the bases of 
the first and fifth ; these four are very large and nearly equal; the fifth is considerably smaller, 
rounded, and placed a little behind that of the fifth toe ; the sixth begins about the same dis¬ 
tance behind the tubercle of the first toe, but is very long and narrow ; slightly crescentic, (the 
concavity internal) ; it is about one fifth the length of the whole foot; its posterior extremity 
as far from the heel as its anterior is from the base of the middle toes. The entire sole between 
the tubercles is perfectly smooth, without granulation; the toes are transversely ridged beneath. 
56 L 
