The Collaborative International Dictionary of English v.0.48:

Diatomophyceae \Diatomophyceae\ n.
   a class of marine and freshwater eukaryotic algae comprising
   the diatoms.

   Syn: Bacillariophyceae, class Bacillariophyceae, class
        Diatomophyceae.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Diatomophyceae
    n 1: marine and freshwater eukaryotic algae: diatoms [syn:
         Bacillariophyceae, class Bacillariophyceae,
         Diatomophyceae, class Diatomophyceae]