[3] The Weymouthiidae are a paraphyletic family because the Agnostina suborder is nested within it, particularly in the clade that further consists of the genera Mallagnostus, Chelediscus, Tannudiscus and Jinghediscus.

[3] Most taxa in this family are small (1–2 cm or 0.4–0.8 inches long), but this is large for the Eodiscina.

The glabella is wide at its base, normally parallel sided but may taper gently or be at its widest at half length.

The occipital ring may be simple or split into two lateral lobes (e. g. in Chelediscus and Tannudiscus).

The thorax consists of three rings when known (Mallagnostus, Marocconus, Serrodiscus, Tannudiscus and Weymouthia).