xcl V Rodenti A. M AMM ALI A.— Rodenti A. 
Keotoma. — Say and Ord. 
the Beaver carrying its loads upon the tail, and of 
its using the tail as a trowel, etc., are untrue. 'I’lie 
tail is, no doubt, used to a certain extent to press the 
mud into place, and, from its broad surface, is very 
serviceable in swimming. 
Myomorpiia. — Murine Rodents. — IMice-like 
Animals. 
Family— MURID JE. 
The Alice are represented by this family name. 
Mr. Allen, in his valuable Monograph of the series 
in Hayden’s Report on Rodentia, 1877, says; “ With 
the exclusion of Zapus, which, as a type of a sep- 
arate family, will be treated in a separate memoir, 
the family Muridce is represented in North America 
by only two sub-families, Murince and Arvicolinm, 
out of the number of groups into which it is usually 
divided. As represented in North America, and by 
the two sub-families, the family MuridcB has the fol- 
lowing characters: Incisors, ; Premolars, g ; 
Alolars, 5-|-; = f = 16 teeth. 
“ The sub family Murince has rooted molars ; and 
compressed incisors, narrower than deep. 'I'he root 
of the under incisor causes a protuberance on the outer 
side of the mandible, at or near the notch between 
the condylar and coronoid processes. The palate is 
nearly ])lane; the nasals projecting anteriorly.” 
“ In Arvicolince the molars are normally rootless 
(except in Fvolomys), julsmatic, with flat crown and 
serrate periphery. 'I'he incisors are often broader 
than deep. 'I'he root of the incisor causes a jiro- 
tuberance, if any, on the inner side of the mandible, 
at or niRir notch between the condylar and descend- 
ing process. 'I’he palate is highly arched. 'I’he 
nasals are not produced beyond the preniaxillaries.” 
Sub-Family — AIURlNiE. 
Mr. Allen makes tw'o tribes, as follows: “Mures 
and Sigmodontes. 'I’his separation of the Old World 
[Mures] and New World [Sigmodontes) representa- 
tives of the sub-family, seems to us warranted, and 
not alone on geographical grounds ; for a decided 
difference in dentition is found, serving for their im- 
mediate identilication. 
“Mures. — Molars of the upper jaw with the tub- 
ercles in three series. Palate extending back of the 
molars. ( I’alaeogean.)” 'True Rats and Alice of the 
Old World. 
“Sigmodontes. — Alolars of the upper jaw with the 
tubercles in two series. I’alate ending opposite the 
last molars. (Neogean.)” Rat-like animals of the 
New World. 
‘‘The Mures which occur in North America — 
namely, four species of the typical genus AIiis — not 
being indigenous to this country, and being more- 
over among the best known of mammals, are not 
treated here.” 
Tribe— SIGAIODONTES. 
All the Murina: indigenous to America are in- 
cluded under this section. 
This genus embraces Sigmodont Rats of the largest 
size, their general aspect being highly murine. 'J’hey 
are peculiar to North America. 
WOOD RAT [Reotoma floridana, Say and Ord ). — 
'I’liis is in color much like the Norway Rat. It is 
found in the Southern United States and Alexico. 
Specimens are found, also, in Alassachusetts and the 
Aliddle States, and it is common in California. 
DUSKY-FOOTED WOOD RAT [R. fuscipes, Cooper). 
— This is a California species, described by Dr. 
Cooper in 1857. It is regarded as unlike any other 
known form. A singular compression of the tail is 
noticed ; its color, also, is singular, being very dark 
or black, and the feet are dusky. 
FERRUGINOUS WOOD RAT [R. ferruginea, Tomes). 
— -’I'his is about seven and a half inches long, the 
tail being six and a half inches. Its color is a rich 
rusty-red. almost golden-rust color along the sides. 
'I’he whiskers are very long, and jet black at base. 
BUSHY-TAILED WOOD RAT [R. cinerea, [Ord) 
Baird ). — 'This is rather the largest of the genus, be- 
ing nearly eleven inches long. Its habitat is Western 
North America. 
SiGMODON. — Say and Ord. 
'I’he general form of the animals comprising this 
genus is stout and like the Armcolince. 'I'he pelage 
is hispid from the presence of stiff hairs. The ears 
are large and orbicular. 'The profile of the head is 
strongly convex; the muzzle short, obtuse and hairy, 
except the nasal pad. 
COTTON RAT [Sigmodon Mspidus, Say and Ord ). — 
'I'his is found in the Houthern United States and 
Alexico, particularly on the coast region. Godman 
recorded it as Arvicola, Baird as S. berlandieri, and 
Aud. and Bach, as A. texiana. It varies from four 
to six inches in length. The length of tail is from 
to inches. 
IIesperomys. — Waterhouse. 
'The classic term Hesperia, the “land of the west,” 
is incorjjorated with a derivation from Mus, “a 
Alouse,” and made to embrace certain forms of the 
New or Western World that are close representa- 
tives of the true AIus, or murine animals of the Old 
World. A sub-genus is instituted as follows : 
Sub-Genus — Vesperimus. — Goues. 
Dr. Cones, from whose Alonograph we extract the 
present matter (Hayden’s Report on Rodentia, 1877), 
says: “ AVe restrict our term vesperimus to leucopns 
and its immediate North American allies. As inti- 
mated before, it is exactly equivalent to IIesperomys 
of Baird, as limited by that author. * * * The 
only other name, except IIesperomys, that we can 
find has been applied to the present sub-genus, is 
Musculus of Rafinesque ; that name, in strict tech- 
nical conformity with the rules of nomenclature, 
ought to be adopted ; * * * but the name is so 
inseparately connected with Mus musculus that to 
use it in a different connection, and one when the 
