The cryptomonads (cryptomonadida, cryptophyta) are a group of tiny flagellates including mostly algal forms. The cells are only around 10-20 μm in size and flattened in shape, with an anterior groove or pocket containg refractile ejectosomes. There are typically two slightly unequal flagella inserting nearly parallel next to the pocket. The mitochondrion has flat cristae.
Except for a few colorless forms like Chilomonas, most cryptomonads contain a chloroplast. Instead of being contained directly, though, there is a reduced eukaryote symbiotic within the cell, which contains a normal prokaryote chloroplast. In total, then, the chloroplast is bound by four membranes with a tiny nucleus (nucleomorph) contained between the middle two. It typically has chlorophylls a and c, much like the dinoflagellates (with which the cryptomonads were formerly grouped) and stramenopiles.
A few cryptomonads have reached the palmelloid stage of organization, but the vast majority are free-living flagellates, and are common in nutrient rich water. Well-known examples include Cryptomonas and Chilomonas.