MOLLUSCOIDA 



189 



Genera 



Suborder 



CTENOSTOMATA 



(Horny or gelatinous zoozcia, having 

 tooth-like processes which close the 

 apertures when the tentacles are 

 retracted) 



IAlcyonidium 

 Vesicularia 



Species 

 A - ramosum 



A. parasiticum 

 V. custata 



Subclass 

 Entoprocta 



(Excretory opening within lophophore ; mouth near margin of area, rvhich is surrounded by 

 tentacles ; tentacles roll up instead of being retracted) 



PediceUina 



P. americana 



