Acidiscus[2] is a genus of eodiscinid trilobite belonging to the family Weymouthiidae Kobayashi T. (1943),[3] Order Agnostida Salter (1864).

Both of these features have been considered as being diagnostic of Acidiscus (e.g., Rushton, 1966; Rasetti, 1966;) but they are shared with Bolboparia.

Synapomorphies of Bolboparia include a sharply tapered and pointed glabella, no occipital spine, tubercles confined to posterior part of the cephalic border, strongly inflated genae, and a sculpture of tightly packed coarse granules.

Among genera currently assigned to Weymouthiidae Kobayashi, 1943 (Jell in Whittington et al. 1997), Rushton (1966, p. 12) noted that, “Acidiscus Rasetti differs from Serrodiscus but slightly”, although several of the characteristics in the former genus that he listed, include the preoccipital glabellar and anterolateral cephalic spines, and the configuration of the lateral glabellar furrows.

A. birdi occurs in association with other Weymouthiidae (Acimetopus, Analox, Bathydiscus, Bolboparia, Leptochilodiscus, Serrodiscus), Calodiscus, several species of Olenellus, and Bonnia (Dorypygidae).