In the Limnadiidae (Fig. 4, C) the telson is laterally compressed and produced, on each side of the anus, into a flattened, upwardly curved process, sharply pointed posteriorly, and often serrate; the anal lobes are represented by two stout curved spines, while in place of the dorsal prolongation of _Lepidurus_ we find two long plumose setae above the anus. In the characters of the telson and anal lobes, as in those of the head, the Limnadiidae approximate to the Cladocera. In _Limnetis brachyura_ the ventral face of the telson is produced into a plate projecting backwards below the anus, in a manner which has no exact parallel among other Crustacea. The =appendages= of the Phyllopoda are fairly uniform in character, except those affected by the sexual dimorphism, which is usually great. [Illustration: FIG. 5.—_Chirocephalus diaphanus_, male. Side view of head, showing the large second antenna, _A_{2}_, with its appendage _Ap_, above which is seen the filiform first antenna; _D.O_, dorsal organ; _E_{1}_, median eye. ] [Illustration: FIG. 6.—_Chirocephalus diaphanus._ Second antenna of male, uncoiled. ] Of the cephalic appendages, the first antennae are generally small, and are never biramous; in _Branchipus_ and its allies they are simple unjointed rods, in some species of _Artemia_ they are three-jointed, in _Apus_ they are feebly divided into two joints, while in _Estheria_ they are many-jointed. The second antennae are the principal organs of locomotion in the Limnadiidae, where they are large and biramous; in all other Phyllopoda they are uniramous in the female, being either unjointed triangular plates as in _Chirocephalus_ (Fig. 2), or minute vestigial filaments as in _Apus_, in which genus Zaddach, Huxley, and Claus have all failed to find any trace of a second antenna in some females. In the male Branchipodidae the second antennae are modified to form claspers, by which the female is seized, the various degrees of complication which these claspers exhibit affording convenient generic characters. In _Branchinecta_ each second antenna is a thick, three-jointed rod, the last joint forming a claw, while the second joint is serrate on its inner margin; in _Branchipus_ the base is much thickened, and bears on its inner side a large filament (perhaps represented by the proximal tubercle of _Branchinecta_ and _Artemia_), which looks like an extra antenna. In _Streptocephalus_ the terminal joint of the antenna is bifid, and there is a basal filament like that of _Branchipus_; in _Chirocephalus diaphanus_ (Figs. 5, 6) the main branch of the antenna consists of two large joints, the terminal joint being a strong claw with a serrated process at its base, while the proximal joint bears two appendages on its inner side; one of these is a small, subconical tubercle, the second is more complicated, consisting of a main stem and five outgrowths. The main stem is many-jointed and