128 
NATURAL HISTORY. 
[n. zool. gal. 
Ord. IV. Glires. 
Fam. 1. Murid a;. 
1. Murina. 
a. Mus. 
Hesperomys. 
Pseudomys. 
Cricetomys. 
Cricetus. 
Dendromys. 
Akodon. 
Hapalotis. 
b. Perognathus. 
2. Arvicolina. 
c. Mvstromys. 
Rhombomys. 
Psammomys. 
Gerbillus. 
Euryotis. 
Otomys. 
d. Sigmodon. 
Neotom a. 
'^“•Eiismodon. 
Reithrodon. 
Ctenodactylus. 
e. Myodes. 
Arvicola. 
3. Saccomyna. 
Saccomys. 
Heteromys. 
Dipodoxnys. 
4. Castorina. 
Castor. 
Myopotamus. 
Fiber. {Ondatra.) 
Hydromys. 
5. Echimyna. 
a. Habrocoma. 
Octodon. 
Psammoryctes. 
b. Capromys. 
c. Aulacodus. 
d. Loncheres. 
Nelomys. 
Echimys. 
Cereomys. 
Dactylomys. 
e. Petromys. 
Fam. 2. Histri- 
cida:. 
Alactaga, 
Jaculus. 
b. Meriones. 
2. Cercolabina. 
Erethizon. 
Cercolabes. 
Sphigyurus. 4 . Myoxina, 
3. Vasyproctina. Myoxus. 
Dasyprocta. ^'^-Glaphiurus. 
Caelogemys. Eleomys. 
4. Hydrocherina . 
Hydrochserus. 
5. Caviirta. 
Cavia. 
Kerodon. 
Glis. 
5. Sciurina. 
« Pteronys. 
Sciuropterus. 
Sciurus. 
Macroxus. 
Fam. 3. Leporidje. Tam&s. 
Lepus. 
Cuniculus. 
Lagomys. 
Fam. 4. Jerboida:. 
1. Cinchillina. 
Cinchilla. 
Lagotis. 
Lagostomus. 
2. Pedestina. 
1. Histricina. 
Histryx. 
Sminthus. Antherura. 
'^^Pedestes. 
3. Dipina. 
a. Dipus. 
Spermophilus. 
Arctomys. 
? Cheiromys. 
Fam. 5. Aspala- 
cida:. 
Spalax. 
Siphneus. 
Chtonoergus. 
Georhychus. 
Bathyergus. 
Saccophilus. 
Apludontia. 
Ctenomys. 
Rhizomys. 
The Table Cases contain the continuation of the collection of Ra¬ 
diated Animals, consisting of such as are covered with a smooth skin; 
in some the outer skin is hardened into a sheath for the protection of 
the contractile body of the animal, while in others the body of the ani¬ 
mal itself, as it enlarges in size, is gradually transformed into a hard and 
stony coral, by the continual deposition of earthy particles into the older 
part of its substance. 
This division (Leiodermata) contains three classes; the Acalepha 
or Sea Nettles, the Zoophytes , and the Polyzoa. 
The first class of Acalepha, or Blubber-fishes , are so called from 
their being almost entirely formed of a soft, very cellular, jelly-like sub¬ 
stance, which rapidly decomposes after death, without leaving any hard 
part or skeleton that can be preserved in a dry state ; they are destitute 
of any true stomach, but only have vesicles in their substance. They 
float free on the ocean. A few animals, which appear to be interme¬ 
diate between them and the Sea Anemonies, as the Porpita and Velella , 
have a cartilaginous plate sunk in their back, which keeps them of a de¬ 
fined form. The plate of the Porpita ( Case 1) is circular and simple, 
while that of the Velella ( Case 1) is oblong, with an erect crest placed 
obliquely across its back. 
Cases 1 to 30 are occupied with the hard parts of the second class, or 
Zoophytes, ( Zoophyta ,) which are so called because these animals are 
often crowded together in societies or families, in such a manner as to 
assume the form of trees. This form is taken to allow each of the in¬ 
dividuals of which the society is composed to procure a fair and equal share 
of nourishment from the water which surrounds them, and on which they 
live, as the leaves of trees extract nourishment from the air in which the 
plant grows. 
