Rhizochromulina's fellow Dictyophyceans include the silicoflagellate Dictyocha, a 'heliozoan'.    From Wordnik.com.  [Research Blogging - All Topics - English] Reference

(1986) Sodium-calcium action potential associated with contraction in the heliozoan.    From Wordnik.com.  [PLoS ONE Alerts: New Articles] Reference