1. Species Trigonium arcticum (Brightwell) Cleve, 1868
2. Species Trigonium inelegans (Greville) A.Mann
3. Species Trigonium pseudonervatum (Grove & Sturt) Hustedt, 1959 accepted as Triceratium pseudonervatum E.Grove & G.Sturt, 1887 accepted as Entogoniopsis pseudonervata (E.Grove & G.Sturt) J.Witkowski, P.A.Sims, N.I.Strelnikova & D.M.Williams, 2015 † (synonym)
4. Species Trigonium tabellarium (T.Brightwell) A.Mann, 1907 accepted as Entogoniopsis tabellaria (T.Brightwell) J.Witkowski, P.A.Sims, N.I.Strelnikova & D.M.Williams, 2015
5. Species Trigonium adspersum Mann, 1907 (uncertain > unassessed)
6. Species Trigonium alternans (Bailey) A.Mann, 1907 accepted as Triceratium alternans f. alternans J.W. Bailey, 1851 (uncertain > unassessed)
7. Species Trigonium bicoronatum (Castracane) Mann, 1925 accepted as Stictodiscus bicoronatus var. bicoronatus Castracane, 1886 (uncertain > unassessed)
8. Species Trigonium caelatum (Janisch in Schmidt et al.) Mann, 1925 accepted as Triceratium caelatum Janisch, 1885 (uncertain > unassessed)
9. Species Trigonium cinnamomeum (Greville) Mann, 1907 accepted as Triceratium cinnamomeum var. cinnamomeum Greville, 1863 (uncertain > unassessed)
10. Species Trigonium condecorum (Ehrenberg) Hendey (uncertain > unassessed)
11. Species Trigonium contumax Mann, 1925 (uncertain > unassessed)
12. Species Trigonium coscinoides (Grove & Sturt) Mann, 1907 accepted as Triceratium coscinoides var. coscinoides Grove & Sturt, 1886 (uncertain > unassessed)
13. Species Trigonium diaphanum A.Mann, 1925 (uncertain > unassessed)
14. Species Trigonium dissimile (Grunow in Schmidt et al.) Mann, 1925 accepted as Triceratium dissimile Grunow in Schmidt et al., 1885 (uncertain > unassessed)
15. Species Trigonium dobreeanum (G.Norman ex Greville) Hustedt, 1959 accepted as Triceratium dobreeanum var. dobreeanum Norman ex Greville, 1865 (uncertain > unassessed)
16. Species Trigonium dulce (Greville) Mann, 1925 accepted as Triceratium dulce var. dulce Greville, 1866 (uncertain > unassessed)
17. Species Trigonium eulensteinii (Grunow in Schmidt et al.) Mann, 1925 accepted as Triceratium eulensteinii var. eulensteinii Grunow in Schmidt et al., 1882 (uncertain > unassessed)
18. Species Trigonium formosum (Brightwell) Cleve, 1867 accepted as Triceratium formosum f. formosum Brightwell, 1856 (uncertain > unassessed)
19. Species Trigonium frauenfeldii (Grunow in Van Heurck) Mann, 1925 accepted as Triceratium frauenfeldii Grunow in Van Heurck, 1883 (uncertain > unassessed)
20. Species Trigonium geminum (Schmidt in Schmidt et al.) Mann, 1925 accepted as Triceratium geminum Schmidt in Schmidt et al., 1882 (uncertain > unassessed)
21. Species Trigonium glandiferum (Grunow) Hustedt, 1959 accepted as Triceratium glandiferum Grunow, 1888 (uncertain > unassessed)
22. Species Trigonium graeffeanum (Witt) Hendey, 1971 (uncertain > unassessed)
23. Species Trigonium hertleinii (Hanna) V.A. Nikolaev & E. Fourtanier in Nikolaev, V.A., Kociolek, J.P., Fourtanier, E., Barron, J.A. & Harwood, D.M., 2001 accepted as Triceratium hertleini Hanna, 1927 (uncertain > unassessed)
24. Species Trigonium heteroporum (Grunow in Van Heurck) Mann, 1925 accepted as Triceratium heteroporum Grunow in Van Heurck, 1883 (uncertain > unassessed)
25. Species Trigonium inglorium (Greville) Mann, 1925 accepted as Triceratium inglorium Greville, 1865 (uncertain > unassessed)
26. Species Trigonium latum (Grev.) A. Mann, 1925 accepted as Triceratium latum var. latum Greville, 1865 (uncertain > unassessed)
27. Species Trigonium membranaceum (Cleve) Mann, 1925 accepted as Biddulphia membranacea Cleve, 1878 (uncertain > unassessed)
28. Species Trigonium moronense (Greville) Desikachary, 1989 accepted as Triceratium moronense var. moronense Greville, 1865 (uncertain > unassessed)
29. Species Trigonium multiplex (Janisch in Schmidt et al.) Mann, 1925 accepted as Triceratium multiplex f. multiplex Janisch in Schmidt et al., 1882 (uncertain > unassessed)
30. Species Trigonium oamaruense (Grove & Sturt) Mann, 1937 accepted as Triceratium oamaruense var. oamaruense Grove & Sturt, 1887 (uncertain > unassessed)
31. Species Trigonium parallelum (Ehrenberg) Mann, 1907 accepted as Amphitetras parallela Ehrenberg, 1840 (uncertain > unassessed)
32. Species Trigonium pardus (Schmidt in Schmidt et al.) Mann, 1925 accepted as Triceratium pardus Schmidt in Schmidt et al., 1882 (uncertain > unassessed)
33. Species Trigonium planoconcavum (Brun in Brun & Tempère) Mann, 1907 accepted as Triceratium planoconcavum var. planoconcavum Brun in Brun & Tempère, 1889 (uncertain > unassessed)
34. Species Trigonium punctatum (Brightwell) A.Mann, 1925 accepted as Triceratium punctatum f. punctatum Brightwell, 1856 (uncertain > unassessed)
35. Species Trigonium radfordianum (Castracane) Mann, 1925 accepted as Stictodiscus radfordianus Castracane, 1886 (uncertain > unassessed)
36. Species Trigonium reticulum (Ehrenberg) Simonsen, 1974 accepted as Triceratium reticulum f. reticulum Ehrenberg, 1844 (uncertain > unassessed)
37. Species Trigonium rusticum Mann, 1907 (uncertain > unassessed)
38. Species Trigonium sculptum (Shadbolt) Mann, 1907 accepted as Triceratium sculptum var. sculptum Shadbolt, 1854 (uncertain > unassessed)
39. Species Trigonium striolatum (Ehrenberg) A.Mann, 1907 accepted as Triceratium striolatum Ehrenberg, 1840 (uncertain > unassessed)
40. Species Trigonium trinitas (Brun in Schmidt et al.) Mann, 1907 accepted as Triceratium trinitas var. trinitas Brun in Schmidt et al., 1891 (uncertain > unassessed)
41. Species Trigonium zonulatum (Greville) Mann, 1907 accepted as Triceratium zonatulatum f. zonulatum Greville, 1865 (uncertain > unassessed)

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