They possessed well-developed, large compound eyes and were believed to have dwelled in shallow-water sediments in life.

[3][4] The body is oblong-oval, about twice as long as it is wide,[5] It had a strongly convex profile, giving it its distinctive globular appearance.

[11] The cephalon is effaced (smooth and mostly featureless), an evolutionary trend also seen in Illaenus and Trimerus, though not as pronounced as that of Bumastus.

This, along with the rounded contours of their body, suggests that Bumastus may have spent most of its time buried in sediment with its eyes protruding.

[13] The rounded smooth shape of Bumastus, as well as the almost complete effacement of its cephalon, is believed to have been an adaptation for burrowing.

They are situated in such a way that they provide the trilobite with a semicircular field of vision on each side, keeping them aware of movements near them.

Enrollment protects the softer body parts below the exoskeleton, while the spherical shape offers the least resistance to wave action.

[5][15] They can also be found in the Ordovician formations of Australia, Canada, China,[19] the Czech Republic, the Russian Federation, Spain, the United States; with specific occurrences from the Dobrotivian age/stage (Llandeilo age) of China and France, and the Whiterockian stage of the United States.

The type species, Bumastus barriensis was recovered from the Coalbrookdale Formation of the Wenlock Group in England.

But he noted the almost absent trilobation of body and the difference in the number of segments in the thorax (10 in B. barriensis and 8 in Isotelus).