Original description: Test wide, conical, with six to eight post-abdominal chambers. Cephalis conical to dome-shaped without horn. Cephalis, thorax, and abdomen imperforate, covered with layer of microgranular silica and separated from each other by one row of small pores. All post-abdominal chambers lobated, closely spaced, gradually increasing in width and length as added. Abdomen and subsequent chambers separated from each other by smooth, perforated circumferential ridges. Ridges usually with two to four rows of small irregular polygonal pore frames, inner latticed layer of test comprised of larger, irregular polygonal pore frames, outer layer of microgranular silica imperforates at constricted median band of earlier post-abdominal chambers, perforated with small polygonal pore frames at final three or four post-abdominal chambers.

Original remarks: Canoptum artum n. sp. differs from Canoptum poissoni Pessagno by having a wider test with a larger cephalis and more closely spaced post-abdominal chambers, and by having an outer layer of test wall more perforate on final post-abdominal chambers.

Etymology: Artus-a-um (Latin, adj.) close, tight.

Canoptum artum was named by Yeh (1987). Its type specimen is NMNS (000071) and is a 3D body fossil. Its type locality is Suplee-Izee area, OR-589D, which is in a Toarcian marine mudstone/limestone in the Snowshoe Formation of Oregon.