An order of the protozoan class Phytamastigophor­ea. This order of protozoa is also known as Euglenoidina, and botanists classify the group in the class Euglenophyceae. The euglenids include the largest green noncolonial flagellates, Euglena ehrenbergii, which are 400 micrometers long. Many of the colorless members are also large. They have one or two equal or subequal flagella. There are relatively few genera of Euglenida, even if doubtful ones such as Clorachne and Ottonia are included. The fresh-water genera Euglena, Lepocinclis, Phacus, and Trachelomonas have many species, as does the colorless genus Petalomonas. Others have few species, including the marine genus Eutreptia. Calkinsia is yellow, some euglenas are red at times, and all others are green or colorless, although Trachelomonas tests are frequently colored by iron.