Hydrosoma bilaterally developed. Branches regular, always furnished only with a single series of hydrothecæ (Monoprionidian). Hydrothecæ rectangular, touching one another, their inferior margin slightly curved. Sicula generally persistent; its free, pointed, downwardly directed end at the proximal extremity of the hydrosoma.

In 1851 M Coy (Brit. Pal. Foss. p. 9) proposed the generic name Didymograptus for two-branched species with one row of cells “sometimes on the inner, sometimes on the outer side of the branches.” Nearly at the same time Geinitz established his genus Cladograptus to include all two-armed or furcate Graptolites.