Although the Carboniferous Trilobites are but few in number, and are all included in four genera, they have not escaped the usual trouble arising from incorrect determinations.

One of these occurred in reference to Phillipsia gemmulifera. Phillips, sp., better known by the name of “Phillipsia pustulata,” Schlotheim species, a name first applied to this form by Professor de Koninck in 1842–44 (see Descr. Anim. Foss. Terr. Carbonif. de Belgique, p, 603, tab. liii. fig. 5).

This Trilobite, first known by a pygidium only, was very carefully figured in " Brongniart′s and Desmarest′s Histoire Naturelle des Crust. Foss. 1823, p. 145, pl. iv. fig. 12, 1822," where it is called “Asaphus” from the black limestone in the environs of Dublin.

It was next figured by Phillips in his Geology of Yorkshire, 1836, vol. ii. pl. xxii. fig. 11, p. 240, who named it Asaphus gemmuliferus.

Buckland again repeats the figure later in the same year, and follows Phillips′s name of A. gemmuliferus.