TELSON OF PHYLLOPODA 



23 



the telson carries two flattened backwardly - directed plates, 

 one on eacli side of tlie anus, the margins of each plate being 

 fringed witli j)limiose setae. In Artcmia the anal plates are 

 rarely as large as in Branchip^is, /dnd 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. urmiana from Persia the 

 anal lobes are well developed in the male, each lobe bearing a 



A 



Fir;. 



4. — A, Ventral view of the anal region in Artemia fertilis, from the Great Salt 

 Lake ; B, ventral view of tlie telson and neighbouring parts of Lejjidurus jM'oductus ; 

 C, side view of the telson and left anal lolie of Estheria (sp. ?). 



single terminal hair, Init 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 A-pus the anus is terminal, 

 but in Lepidurns (Fig. 4, B) the dorsal part of the telson is 

 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- 



