^uw?^.^(Hmi.J^Sci.fI^42/.sM.l9. 



(J 



z: 



> 



_i in 

 a. 



o 

 to a: 



Compound 

 Melanoid ^roup 



Terrestial 



< < Freshwater 

 <-> \ Marine 



Q 

 O 



q: 



LU 



Q. 



Scheme shewing the apparent phylogenetic origin 

 of some existing fresh-water groups. 



r.Huth,Lith''Edin'' 



