Family: Cirri in 2 marginal, 1 frontoventral files; cirral files straight;
more than 1 frontoventral file extends past middle of body (Illustrated Guide, 1985).
Genus: Elongate, some species with a pronouced head region; body often twistes and flexes during locomotion; three rows of ventral cirri (2 rows of marginal cirri, 1 row of ventral cirri from Curds, 1982); frontal & V-shaped transverse cirri; transverse cirri may be very long extending beyond the posterior (Carey, 1992).
A. thiophaga (Kahl, 1928) Kahl, 1930-5: Elongate; 100 μm long; AZM 1/3 of the body length; transverse cirri project beyond the posterior; only 5 frontal cirri; two ovoid macronuclei; lateral stiff cirri absent (?) (Carey, 1992).