10 
BRITISH ENTOMOSTRACA. 
Monoculi and Binoculi. Brisson, however, in his ‘ Regne 
Animal/ * as early as 1756, had formed a distinct class 
for the Crustacea, of which the Entomostraca formed a 
part ; and Cuvier and Latreille, in their second Methods, 
and in their subsequent publications, and all succeeding 
authors, have adopted this arrangement, and have con- 
tinued to place the Entomostraca with the great family 
Crustacea, apart from the Insects. 
Latreille, in his ‘ Hist. Nat. gen. et part, des Crust./ 
1802, divides the great class Crustacea into two sub -classes, 
the Entomostraca and Malacostraca. The Entomostraca 
he subdivides into two sections — Thecata, those inclosed, 
1st, in a shield- shaped, or, 2d, in a bivalve-formed shell or 
covering, and Gymnota, those in which the body is nearly 
or entirely naked. The Thecata he divides into four orders, 
the Xiphosura and Pneumoneura, corresponding nearly to 
the Binoculi of his first arrangement, and the Phyllopoda 
and Ostracoda corresponding in part to his Monoculi. 
The Gymnota he divides into two orders, the Pseudopoda 
and the Cephalota, which include the remainder of his 
Monoculi. In his ‘ Gen. Crust, et Insect./ 1806, and in 
his ‘ Consid. generales/ 1810, he follows the same ar- 
rangement ; and Leach, in the ‘ Edinburgh Encyclopaedia,’ 
and again in the Supplement to the ‘ Encyclopaedia 
Britannica/ adopts, in his articles on the Entomostraca, 
one precisely similar, taking as the basis of his subdivisions 
the covering or shell in which the animal is contained. 
In the ‘Diet. des Sc. Nat./ 1819, this naturalist adopts, 
however, the structure of the feet as the basis of sub- 
division. He forms four orders : 1st, Paecilopoda, where 
the feet in front are formed to walk and lay hold with, 
and the others for swimming ; 2d, Phyllopoda, where the 
front feet are formed like antennae, terminated by long- 
setae, and the others formed for swimming ; 3d, Lophy- 
ropoda ; and, 4th, Branchiopoda, in which all the feet are 
formed for swimming. 
* Lc Iteg’nc Animal, divis. cn 9 Classes, &c. 
