a. [Erroneous formation for TRIGONAL, after tetragonal, pentagonal, etc.; cf. TRIALOGUE.] Triangular.
1822. Scott, Pirate, xv., note. They change ranks, and place themselves in a triagonal figure.
1879. Proc. U. S. Nat. Museum, II. 270. Ostracionts with triagonal, tetragonal, or pentagonal carapaces.
