THE FIRST ORDER OF ENTOMOSTRACA, 
OR SIXTH OF THE CLASS OF CRUSTACEA. 
THE BRANCHIOPODA. 
The characters of this order are, a mouth composed of a 
labrum, of two mandibles, of a ligula, and of one or two pairs 
ofjaws; gills — or the first of these organs, when there are se- 
veral — always anterior. 
These Crustacea are invariably erratic, generally covered 
by a testa in the form of a shield, or of a bivalve shell, and 
provided with four or two antennas. Their feet, with some 
few exceptions, are solely adapted for swimming. The num- 
ber of their feet varies ; in some it is only six, in others, from 
twenty to forty-two, or even more than a hundred. Many of 
these animals have but a single eye. 
The majority of these Crustacea, being, as we have already 
observed, almost microscopical, it is obvious that the applica- 
tion of one of the characters which we have hitherto em- 
ployed, namely the presence or absence of mandibulary palpi, 
would, under such circumstances, present difficulties almost 
insurmountable. We shall, however, place at the head of the 
entomostraca, all the branchiopoda whose mandibles are pro- 
vided with palpi. They will compose the first two divisions 
of the lopliyropa ; but the form and the number of the feet, 
number of the eyes, and the testa, will furnish us with charac- 
ters more easily to be employed, and more within the reach 
of general observation. 
The order of the branchiopoda in the methods of Degeer, 
