Genus Trisidos P. F. Roding, 1798

(3-7-3-0-1-1-2-86-0-0-0-0-0)
Ref. Abbott & Dance, 1984 p 294
Lindner, 1977 p 99
Syn. Epitrisis T. Iredale, 1939;
Parallelepipedum O. A. L. Morch, 1850;
Trisis L. Oken, 1815
Ref. Vaught, 1989 p 115
Syn. Parallelepipedum H. & A. Adams, 1857;
Trysidos F. Paetel, 1890
Ref. Vokes, 1980 p 13

semitorta (J. B. P. A. de Lamarck, 1819)
(3-7-3-0-1-1-2-86-0-1-0-0-0)
Half-propellor Ark
Ref. Abbott & Dance, 1984 p 294 c

torta (O. A. L. Morch, 1850)
(3-7-3-0-1-1-2-86-0-2-0-0-0)
Twisted Ark
Ref. Abbott & Dance, 1984 p 294 c

tortuosa (C. v. Linne, 1758)
(3-7-3-0-1-1-2-86-0-3-0-0-0)
Propellor Ark
Ref. Abbott & Dance, 1984 p 294 c