EUASTRUM. 63 



very prettily denticulated at the margin, besides 

 the deeper divisions - 9 and the white edge, and 

 bright green centre, are strikingly beautiful. 

 M. crenata is smaller, and less denticulated. 

 M. rotata is large, and with, two of the divisions 

 cut in a curved line. There are several other 

 species, but they are rare. 



Euastrmn somewhat resembles the last genus, 

 but the species are more oblong in form, and 

 have circular protuberances on the surface. They 

 are attractive, also, from their size. Uuasfmm 

 oUongum (Drop I. fig. 3) is common in pools : the 

 form of it is much longer than broad, with five 

 or six prominences. Euasirum inslgne is smaller, 

 has the segments inflated at the base, and taper- 

 ing into the form of a neck, with the end a little 



