Dysteriidæ (dist or i ide)

pl. [NL., ra ed. They have the carapace simple or consisting of two lateral, subequal, conjoined, or detached valves; cilia confined to the more or le narrow or constricted ventral surface; the oral aperture followed by a distinct pharynx, the walls of which are strengthened by a simple horny tube, by a cylindrical fascicle of corneous rods, or by otherwise differentiated corneous elements; a conspicuous tail-like style, or compact fascicle of setose cilia presenting a style-like aspect, projecting from the posterior extremity. Most of them inhabit salt water.