BRANCHIOPODA. 441 



varyino; accordinj!: to the length of their oars and the breadth of their shells. According to Strauss, their food con- 

 sists exclusively of minute particles of vegetable substances, which they meet with in the water, and often of 

 conferva. They constantly refused the animal matter he gave them. It is by the action of their legs that they pro- 

 duce a current on the water, which brings their food towards the mouth. The hooks at the tip of the tail are 

 used in cleaning the branchiae. [Mr. Baird has published a detailed account of the anatomy and habits of this 

 genus in the second volume of the Magazine of Zoology and Botang.'] 



The most common species is D. pule.r, (Monoculus pulex, Liim. ; Pule.r aquaticus arborcscens, SAvammerdam), 

 or the arborescent water-flea. It has the setae of its oars plumose ; its valves are notched on the lower edge, and 

 terminated by a short tail, which is obtuse in the females. 



The last subgenus is i(/nce««,Muller {Cliilodorus, Leach), distinguished by the oars being shorter than the shell, 

 and of which tlie lower part does not form a produced point. All the species have in front of the eye a small 

 black spot, having the appearance of a second [frontal] eye. 



The secoiid section of the Branchiopoda — that of the Phyllopa — is distinguished from 

 the former by the number of feet, which is at least twenty,* and m some much more con- 

 siderable ; their joints, or at least the terminal ones, are flattened, lamellar, or foliaceous, and 

 cihated. The mandibles are destitute of palpi. They have two eyes, (situated in some at 

 the extremity of two moveable peduncles,) and some have also an ocellus ; the antenna;, of which 

 there are generally only two, are small, and not fitted for swimming. These Crustacea compose 

 two principal groups. 



1. The Ceratopthalma, Latr., have at least ten pair of legs, and at the most twenty-two pairs, 

 without any vesicular appendages at their base, and of which the anterior are never much longer than 

 the others, nor ramified. The body is inclosed in a shield, formed Uke a bivalve shell, or naked, with 

 each of the thoracic divisions bearing a pair of exposed feet. The eyes are sometimes sessOe, small, 

 and close together, but more commonly they are situated at the extremity of two moveable peduncles. 

 The eggs are internal or external, and inclosed in a capsule at the base of the tail. 



In some species the eyes are sessile, immoveable, and the body inclosed in a bivalve shell ; the 

 ovaries are always internal. They form the genus 



Limnadia of Ad. Brongniart, which so nearly approach the preceding that Hermann placed the only species 

 known [to him and Latreille] amongst the Daphniae. The shell is oval, bivalve, and incloses the body, which is 

 long, linear, and inflected in front. Upon the head are placed, 1, two eyes in a transverse direction, and close to- 

 gether; 2, four antennae, two much longer than the others, each composed of an 8-jointed peduncle, and two 

 8-jointed setaceous branches, rather silky, and two others intermediate in situation, small, simple, and dilated at 

 the tips; 3, the mouth, situated beneath, consisting of two mandibles, swollen, curved, and truncate at the 

 inferior extremity, and two foliaceous maxillfe. These parts form together a kind of beak, placed beneath. The 

 body, properly so called, is divided into twenty-three segments, each of which (except the last) bears a pair of 

 branchial feet. All these feet are alike, very compressed, bifid, with the outer division simple, ciliated at the 

 outer edge, and the other 4-jointed, and strongly ciliated on the inner edge. The twelve fore pairs of legs are of 

 the same length, and longer than the others, which diminish gradually in length. The eleventh, twelfth, and 

 thirteenth pairs have at the base a slender filament, bent upwards into the cavity between the back and the shell, 

 serving as the support for the eggs. The ovaries are internal, and situated at the sides of the intestinal canal. 

 The eggs, after being laid, occupy the dorsal cavity above noticed, and are there attached by means of small fila- 

 ments adhering to those of the supports. They are at first round and transparent, but afterwards become 

 darker, and irregular in shape. All the individuals observed by Brongniart were provided with them, so that the 

 males remain unknown (if there are individuals of that sex), and are supposed to appear at a different season from 

 the females. The type, Limnadia Ilermanni (A. Brongniart, Daphina gigas, Hermann), has been found in small 

 pools of water in the forest of Fontainebleau. 



[M. Guerin has published a monograph upon this genus in his Magasin du Zoologie for 1837, describing three 

 species.] 



[Estheria, Strauss, (Cyzgcus, Audouin,) is a genus closely allied to Limnadia, found in the Red Sea. Type, E. 

 Dahalaccnsis, Ruppell, in Trans. Mus. Seclienberg, 1837.] 



In the other species of Ceratojjthalma, the eyes are placed at the extremities of two long peduncles, 

 formed by the lateral prolongation, like a nose on each side of the bead. The body is naked, not in- 

 closed in a shield, and annulated throughout its entire length. The females carry their eggs in an 

 elongated capsule, placed at the base of the tail when present, or at the posterior extremity of the body 

 and thorax in those which have no tail. 



Artemia, ljis.c\\, has the body terminated by a tail, the eyes borne at the extremity of very short peduncles; 

 the head confluent, with an oval thorax, supporting ten pairs of legs, and terminated by a long and pointed tail. 



* These animals n-picscjit in lUis class of Crustacia the Myriapoda in that of the Insccta. 



