CRUSTACEA. 
436 
Kegne Animal, although Latreille himself, as stated in p. 410, in his more recent work, 
had raised some of those groups, subsequently described, to the rank of orders.] 
THE FIRST ORDER OF ENTOMOSTRACA,— 
{The Sixth of the Class Crustacea), — 
BRANCHIOPODA,- 
Has, for its characters, a mouth composed of an upper lip, two mandibles, a tongue, 
and one or two pairs of maxillae ; and the branchiae, or the first of these organs when 
there are many, always anterior. I 
These Crustacea are always wandering about, generally covered by a shell in the 
form of a shield, or bivalve case, and provided with two or four antennae. The legs, I 
except in a few, are only fitted for swimming : they are variable in their numbers, there 
being only six in some, but in others there are from twenty to forty-two, or even more 
than a hundred. Many exhibit only one eye. 
These Crustacea being for the most part microscopical, it will be perceived that the 
application of one of the characters of which we have made use — namely, that of the ** 
presence or absence of mandibular palpi — will here present nearly insurmountable dif- 
ficulties.* The form, and the number of the legs and eyes, the shell and the antennae, 
will furnish characters of more ready application, and capable of being examined by 
every inquirer. 
The order of Branchiopoda composed, in the methods of De Geer, Fabricius, and 
Linnaeus [with the exception of a single species, M. Polyphemus'], the single genus, 
Monoculus (Linn.),t — 
Which we separate into two principal sections: 1. Lophyropa, divisible into three i 
subsections, Carcinoida, Ostracoda, and Cladocera ; and, 2. Phyllopa, divisible into 
two subsections, Ceratopthalma and Aspidiphora. 
The first section of the Branchiopoda — ih&t of the Lophyropa — is distinguished by 
the number of the legs, which never exceeds ten, and of which the joints are cylindrical or •'j 
conical, and never entirely lamelliform or foliaceous. The branchiae are few in number, and ; 
the majority have only one eye. Many, also, have the mandibles furnished with a palpus. ;« 
The antennae are generally four in number, and are used in locomotion.]; I 
We divide the Lophyropa into three principal and very natural divisions, and of which the j 
two first agree with the preceding Crustacea in their palpigerous mandibles, and some other ^ 
characters. : 
The fii’st division of the Lophyropous Branchiopoda, or that of the Carcinoida, Latr., has the shell 
more or less ovoid, or oval, not shutting in two parts in the manner of a bivalve shell, but leaving the I 
lower part of the body naked. Their antennae have never the appearance of branching arms. The legs | 
are ten in number, and more or less cylindrical, or setaceous. The females in those species whose gesta-ffl 
tion has been observed, carry their eggs in two external sacs situated at the base of the tail. Some o^ 
them have two distinct eyes, and form a first subdivision. H 
Those species which have the thorax entirely covered by the shell, with the eyes large, and the inter^ 
mediate antenme terminated by two filaments, compose the two following genera. 
* We nevertheless arrange, at the head, all those Branchiopoda t Strauss appears to attribute this character exclusively to Cyprisj) 
which have the mandibles furnished with palpi. They compose the and Cythere ; but from the observations of the elder Jurine a^ 
two first divisions of the Lophyropa. Ramdohr, it exists also in Cyclops. ^ 
+ Together with that of Binoculus of Geoffrey. ^ fllj; 
