Eucidaris tribuloides was first described and classified by Jean Baptiste Lamarck in 1816 as Cidarites tribuloides.
The slate pencil urchin can be found on both sides of the Atlantic, and throughout the Caribbean. On the western side of the Atlantic, the slate pencil urchin has been found as far north as Cape Hatteras, North Carolina and as far south as Rio de Janeiro. In the Gulf of Mexico, populations have been reported at Alacran Reef, Campeche Bank. On the eastern side of the Atlantic, a closely related sub-species, Eucidaris tribuloides var. africana, has been reported at Cape Verde Islands, in the Gulf of Guinea, and at the Azores and Ascension Islands.
E. tribuloides has become an invasive species in some parts of the world including Maltese waters where it has been since 1998. This was the first record in the Mediterranean and is thought to have been brought there in ballast water.
McPherson described E. tribuloides as a "sluggish echinoid" that leads a nocturnal, benthic existence. During daylight hours, the slate pencil urchin uses its large primary spines to anchor itself under or atop rocks or to lodge itself in crevices. Individuals rarely stray far from their locality. At night, they will feed primarily on corals and sponges, among other things.