JAPANESE FRESHWATER SPONGES. 



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Shafts of birotulates straight. 



a. Skeleton spicules smooth. Shafts of birotulates much longer 

 than the diameter of the rotulae, which are not deeply 

 indented E. fliiviatilis. 



b. Skeleton spicules smooth. Shafts of birotulates smooth, not 

 much longer than the diameter of the rotulae, which are 

 deeply serrated E . Japoniea. 



c. Some or all the skeleton spicules rough in the middle. 

 Shafts of some of the birotulates bearing spines, of all not 

 much longer than the diameter of rotulae, which are deeply 

 and irregularly serrated E. millleri. 



