Acontheus appears confined to the Drumian and Guzhangian Stages, uppermost two of three Stages subdividing the middle Cambrian Miaolingian Series and, if species assignments are correct, the genus ranges in terms of the Scandinavian sequence from at least the Hypagnostus parvifrons Biozone in Wales to the Lejopyge laevigata Biozone at various locations elsewhere.

also erected Tribe HARTSHILLINI within the Acontheinae to accommodate the highly derived genera Hartshillia Illing, 1916 [8] and Hartshillina Lake, 1940.

16, figures 8a-b, 9; Jago et al.., 2011, p. 29), although according to some authors including species with proparian sutures and possibly small palpepral lobes (see Remarks).

Growth stages of Acontheus from the Menevia Formation (H. parvifrons Biozone) of Porth-y-rhaw, St. David's, are housed in the National Museum of Wales, Cardiff - collection prefix 80.34G.

Hutchinson (1962, p. 109) noted that the ‘cranidium’ of A. inarmatus resembles that of the much larger Acontheus acutangulus Angelin, but differs in that the glabella is more strongly expanded frontally, glabellar furrows are weaker, genal spines are lacking (unless a marginal suture had removed the posterolateral border with genal spine) and the glabella and cheeks are punctate rather than smooth.

He also credibly remarked that “according to modern usage, these differences are great enough to warrant generic distinction between the two forms” but nevertheless preferred to retain them in the same genus.

Punctation of the exoskeleton is also slightly less coarse than in A. inarmatus, and the occipital ring is less elevated and without a median node.

nov.; the subspecies especially resembles A. inarmatus in the marked forward expansion of its glabella and small genae, but from the illustrations there is no clear evidence of lateral glabellar furrows as seen in Hutchinson's species.

than in the Swedish species and terminates slightly short of the posterior border furrow, whereas in both A. acutangulus Angelin, 1851 and A. sp.

nov., the axis actually meets the border furrow and separates the pleural fields, as also observed in Clavigellus annulus Geyer (1994, figs.

nov., however, it is clearly the interpleural furrows that give the pygidial border its lobed character and, without rearward deflection as observed in the type species, A. cf, acutangulus, Jago et al. (op.

The pygidium is of similar design to that of the type species and if compared on its own could be regarded as congeneric, differing specifically from other forms in having one more rib and axial ring.

1) appears to possess a straight lateral margin which he tentatively suggested to be a proparian suture that separates a narrow librigena.

The specimen appears also to have an ocular ridge extending possibly to a small palpebral lobe, though Öpik did not represent eyes in his reconstruction (text-fig.