PITH OF THE PERIODICALS. 193 



Of the Entomostracous orders he gives the following cha- 

 racters : — 



Order. — Lopiiyropa. 



From the observations of Rhamdohr, &c. it appears that the 

 last pair of thoracic feet in these Enlomostraca correspond 

 with the third pair in the A mphipoda and Isojwda, and to the 

 first pair in the Decapoda. According to J urine, the number 

 of thoracic feet is eight, but we observed, from the succession of 

 the appendages which precede them, that those which he has 

 designated by the name of hands answer to the second pair of 

 maxillae, and therefore the three anterior pair of feet, properly 

 so called, represent as many foot-maxillas {pieds-maclwires.) 

 The genus Daphnia has, according to Straus, ten feet, of 

 which the two first answer to the second pair of maxillae. 



First family. — Seticera. The thorax is more or less 

 oval, and divided into four segments, of which the anterior is 

 much the largest, and includes the head, and presents ante- 

 riorly and centrally the organ of vision. The superior 

 antennas are long, setaceous, simple, and composed of nume- 

 rous minute articulations. The inferior antenna? are short, 

 filiform, and simple, or forked ; they seem to have but four 

 articulations. Each mandible bears a feeler, which is some- 

 times entire, at others divided into two branches. Imme- 

 diately behind the organs, answering to the superior maxillae, 

 are five pair of feet, divided into two cylindrical branches, 

 more or less furnished with hair. The tail is composed of 

 six rings, with two spears and bristles at the extremity. 

 Under the first, we observe in the female two appendages, in 

 the form of feet; and under the second, in both sexes the 

 organs of generation, and two oviferous pedunculated sacs. 

 Genus, Cyclops. 



Second family. — Cladocera. Head large, projecting, often 

 terminating below in a beak-like point, and bearing superiorly 

 an eye varying in size, preceded in some species by an oculi- 

 form black spot, and having at its junction with the thorax 

 an antenna always projecting, commonly very large, in the 

 form of an arm, and serving as an oar; it is divided into two 

 or three branches, and furnished with bristles. Testaceous 

 covering folded in two, but without a hinge, enveloping the 

 thorax and feet, and generally terminating in a point at its 



