Thecamoebina

Thecamoebina

 

(also Testacea), an order of protozoans of the class Sarcodina. The cytoplasm and nucleus of the Theca-moebina are similar to those in the Amoebina. The Thecamoebina, however, have a shell 50–150 microns in length, whose cavity contains the greater part of the body, including the nucleus. Only the psuedopodia protrude from the orifice. The shells may be chitinous (Arcella) and are often inlaid with foreign particles (Difflugia). Reproduction is asexual, by means of division. There are several hundred species, which are distributed primarily in the littoral zone of freshwaters.