II TELSON OF PHYLLOPODA PAeh 
the telson carries two flattened backwardly - directed plates, 
one on each side of the anus, the margins of each plate being 
fringed with plumose setae. In Artemia the anal plates are 
rarely as large as in Branchipus, and never have their margins 
completely fringed with setae; in A. salina from Western 
Europe, and in A. fertilis (Fig. 4, A) from the Great 
Salt Lake of Utah, there is a variable number of setae round 
the apical half of each lobe, but in specimens of A. salina from 
Western Siberia the number of setae may be very small, or they 
may be absent; in the closely allied A. wrmiana from Persia the 
anal lobes are well developed in the male, each lobe bearing a 
Fic. 4,—A, Ventral view of the anal region in Artemia fertilis, from the Great Salt 
Lake ; B, ventral view of the telson and neighbouring parts of Lepidurus productus ; 
C, side view of the telson and left anal lobe of Estheria (sp. *). 
single terminal hair, but they are altogether absent in the female. 
Schmankewitch and Bateson have shown that there is a certain 
relation between the salinity of the water in which Artemia salina 
occurs and the condition of the anal lobes, specimens from denser 
waters having on the whole fewer setae; the relation is, however, 
evidently very complex, and further evidence is wanted before 
any more definite statements can be made. 
In the Apodidae the anal lobes have the form of two jointed 
cirri, often of considerable length ; in Apus the anus is terminal, 
but in ZLepidurus (Fig. 4, B) the dorsal part of the telson 1s 
prolonged backwards, so as to form a plate, on the ventral face 
of which the anus opens, much as in the Malacostraca. 
In the Limnadiidae (Fig. 4, C) the telson is laterally com- 
