Family: Frontal cirri differ in size and/or pattern from ventral ones of files; "collar" extends short distance along right edge of body; oral area not U-shaped (Illustrated Guide, 1985). Genus: Many species; usually ovoid or elongate in shape; AZM 1/4 of the body length; two rows of ventral cirri; frontal cirri present (Carey, 1992). Frontventral cirri in zig-zag files; rear rounded, body oval to long (Illustrated Guide, 1985). Species:

50 μm 100 μm 150 μm; x 400

31 μm 63 μm 94 μm; x 640

H. diademata (Rees, 1884) Kahl, 1930-5: Elongate, 140 μm long; a long AZM occupying 1/3 body length; 7 long & stout frontal cirri; two ovoid macronuclei (Carey, 1992).
H. kessleri (Wrzesnioski, 1877) Kahl, 1930-5: Elongate, anterior rounded, but posterior truncated; 150 μm long; AZM 1/4 body length; two groups (?) of ovoid macronuclei (Carey, 1992).