ECHINOIDEA. 243 



genera of the Spatangidce, Micraster (fig. 137, A), Echino- 

 spatagus, Epiaster, and others are Cretaceous ; Hemiaster and 

 Periaster are both Cretaceous and Tertiary ; Gualtieria (fig. 

 138), Macropneustes and Pericosmus are Tertiary; and Spat- 

 angus, Schizaster, Eupatagus, JBrissus, and Brissopsis are repre- 

 sented both in Tertiary deposits and in our recent seas. 



