Rodkntia. MAMMALIA. Rodentia. 
The Ckicktin^ are all OKI World forms. 'I’lie 
true Hamster (Cricetus) is the most familiar species 
common in Middle Europe. 
SiGJiODO.NTES are represented nearly exclusively in 
North America. Ochetodon is now regarded as em- 
bracing both forms, which were formerly placed in 
the genus lleithrodou. These species are given, 
with more particulars, in connection with the genus 
Ochetodon, previously mentioned. 
Of the Hesferomyin.®!, which are so largely North 
American, ^lurray presents thirteen species of Galo- 
mys as exclusively South American. Habrothrix 
has nine species, confined to South America. O.xy- 
mycterus has six species, with the same circum- 
scribed range. 'I'he genera Holochilus, Akodon and 
Drymomys have respectively four, one, and one spe- 
cies, equally confined to the same limits. 
Murray enumerates ninety-eight species of the 
genus Mus — all Old World — forty-five being Asiatic, 
twenty-si.x African, five European, and the remainder 
in the Pacific Islands. None are American ; the 
Common Rat and Mouse being the same-as the Euro- 
pean forms, which have been introduced. 
Of the Murin,e there remain three genera and five 
species, indigenous to South Africa and New South 
IVales. These are the genera Steatomys, Pseu- 
domys and Dendromys. 
'I’he S.MiNTiiix,B have four genera and sixteen 
species, many of them in Africa and Asia ; two are in 
the South Sea Islands. Ilydromys is one of the latter, 
in the marl of Issoire. Ilyrax is placed in the list 
of Rodents by IMurray, and six species are enumerated, 
all from Africa, excepting one from Syria. 
Dasyrrocti.x^. — 'I' he genus Coelogenys has one 
species — the Caca, in South America. 'I'wo fossil 
and extinct species are known in the bone caves of 
Brazil, viz.: C. laticeps and 0. major. Dasyprocta 
agouchy, and six others, are South American. 
EchimyiNvB. — 'I' his is represented by Capromys and 
two species, habitat Cuba; Plagiodonta, one species, 
St. Domingo ; Myopotamus coypus, the notable “ big 
Rat,” or Coypu,” of Brazil ; Cercomys, one 
species; Pteromys, one species; Dactylomys, three 
species; Loncheres, nine species; Mesomys, two 
species; Echimys, five species; and a fossil extinct 
genus, Carterodon — all South American. Aula- 
codus, with one species, is an African genus. 
OcTODONTiN.®. — Habrocoma has two species ; Octo- 
don, one ; Scliizodon, one ; Spalacopus, two ; Cten- 
omys, four — all South American. Wallace places in 
the family Octodontid^e, eight genera and nineteen 
species. 
CniNCUii.LiNiE. — Lagostomys has one species ; 
Lagidium, two ; Chinchilla, two — all South Ameri- 
can. Wallace places three genera and six species in 
the family. 
Caviina:. — T he great Ilydrochoerus belongs to 
this group. One species is known oidy. An ex- 
tinct one, Sulcidens, has been found in the Brazilian 
caves. Dolichotis has one species, Anoema has 
one, and Cavia has ten species, besides three fossil 
extinct forms from the caves of Brazil. 
'i’oxoDONTiD.E. — 'I’liis represents an extinct family. 
cvii 
established to admit a gigantic form of water Rodent, 
larger than the present Capybara. It is closely 
allied to the latter. Andrew Murray regards the 
Hyra.x as “connected with the Capybaras, and, on 
the other hand, with the Pikas and Hares.” Cer- 
tain bones were found by Mr. Darwin, near Bahia 
Blanca, in South America. 'I’he name 'i'oxodon 
platensis has since been applied to the species recog- 
nized from them. 'I'he skull represents a large ani- 
mal for a Rodent, being two feet four inches in 
length, and one foot four inches in breadth. 'I'his 
skull has incisors like those of the Hare ; the princi- 
pal ones being supplemented by an additioLial small 
one directly behind, as in the Hares, 'i'he molars 
were seven in number on each side, “'i'he den- 
tition,” says Prof. Owen, “closely approached the 
Rodent type, and tended to complete the chain of 
affinities which link the Pachydermatous with the 
Rodent and Cetaceous orders.” 'J’he 'I'oxodon is 
supposed to have been twelve or sixteen feet in length. 
A form has lately been described by Prof. Marsh, 
from the Upper Miocene of Oregon, which is re- 
garded as ditierent from any now in existence, called 
Allomys, and thought to be allied to the P'lying 
Squirrels, but having molars somewhat resembling 
those of the Ungulates. 'I'he Pliocene of South 
America furnishes a new genus — Cardiodus. In the 
Post 'i'ertiary the Rodents were very abundant, but 
the species were, in most cases, different from tliose 
now living. 
Pectinatorid/E is represented only in Africa, by a 
few species of two genera. 
Myoxixi has six genera and thirteen species, dis- 
tributed throughout Europe, Asia and Africa. 'I'he 
little Dormouse of England is an example of the 
group. 
LEPORiDyE is represented by thirteen species of 
Rabbits and Hares in Asia, by seven in Europe, 
by five in Africa, and the remainder are found in 
North America, excepting onni species, which is in- 
digenous to South America. About forty species 
are known, included in one genus. 
HiSTRicixaJ. — In this sub-family are embraced 
four genera. Wallace makes three in the family. 
Ch®tomys, with one species, is South American ; 
Cercolabes, with si.x species, is from the same region ; 
and also three fossil extinct species. Erethizon has 
two species or varieties in North America ; Hystrix, 
the typical genus, has seven species, all African. An 
extinct genus — Theridomys — has three species in 
Europe; Meriones is represented in Africa by twenty 
species, and in Europe and Asia by seven species ; 
Mystromys and Otomys, with three and four species 
respectively, are found in South Africa. In New 
South Wales and Australia the genus Hapalotis is 
represented by eleven species. 
Dh'Odixje.— O f this group the genus Dipus, in- 
cluding the Jerboas, has seven species ; two are ex- 
clusively European, and the remainder African. 
Alactaga, of the same group, has eight species. 
Asiatic and African. Jaculus is iXmerican. Wal- 
lace’s family, Dipodidw, includes three genera and 
twenty-two species. 
