ORDER BRANCHIOPODA. 325 



Fabricius, and of Linuseus, was composed, with the omission 

 of a single species (M. Pohjpliemus), only of the genus 



MoNOCULUS, Linn. *, - . 



Which we shall divide into two principal sections. 



The first, that of Lophyropa, is distinguished by the num- 

 ber of the feet, which never exceeds ten. Their articulations, 

 besides, are more or less cylindrical or conical, and never 

 entirely lamelliform or foliaceous. Their gills are not nu- 

 merous, and the majority of these animals have but a single 

 eye. Several, moreover, have mandibles furnished with a 

 palpus. M. Straus, indeed, appears to attribute this character 

 exclusively to cypris and cytherea, which compose his order 

 of ostrapoda ; but the observations of the elder Jurine, and of 

 M. Ramdohr, prove that it is also proper to the Cyclopes. The 

 antennae are almost always four in number, and serve for the 

 purpose of locomotion. 



In the second section, that of Phyllopa, the number of 

 the feet is twenty at least, and in some, much more consider- 

 able. Their articulations, or at least the last ones, are flatted, 

 in the form of ciliated leaflets. Their mandibles never ex- 

 hibit palpi. They all have two eyes, situated in some at the 

 extremity of two movable pedicles. Their antennae, the 

 number of which, in several, is but two, are generally small, 

 and not adapted for swimming. 



We shall divide the Lophyropa into three principal 

 groups, very natural, and the first t\^•o of which approximate 

 to the Crustacea of the first three orders, in consequence of 

 their mandibles having each one palpus, and likewise from- 

 some other characters. 



1st. Those (Carcinoida, Lat.) whose testa, more or less 

 ovoid, or ovaliform, is not bent in two like a bivalve shell, 



* In the system of Geoffrey, the genus Binoculus is induded. 



