[ref. ID; 2014]
Solitary. Elongate body, anterior long and tube-like, posterior usually widens into a bulbous region. Most species are embedded in a gelatinous case to which the posterior end of the cell is attached by a thread. Peristomial disc raised above the rim of the peristome. Macronucleus elongate and ribbon-like. Most easily confused with Ophrydium which is a colonial organism and with Ophrydiopsis which is solitary. Gerda is distinguished from Ophrydiopsis by the depressed peristomial disc and the disc-like scopula in the latter genus.
Quote; Colin R. Curds, Michael A. Gates and David McL. Roberts "British and other freshwater ciliated protozoa Part II Ciliophora: Oligohymenophora and Polyhymenophora" Cambridge University Press, 1983 (ref. ID; 2014)