→Distribution and habitat: The citation does not state they are found at the mid-Atlantic ridge, but nearby islands. Saying they are at the ridge implies a deeper depth than is accurate.
From the [[United States]] to [[Brazil]] on the west to [[Mauritania]] to [[Gabon]] on the east, the slate pencil urchin can be found on both sides of the Atlantic, at the [[mid-Atlantic ridge]] and throughout the [[Caribbean]].<ref name=McPherson1968>{{cite journal | author=McPherson, BF | title=Contributions to the biology of the sea urchin ''Eucidaris tribuloides'' (Lamarck) | journal=Bulletin of Marine Science | volume=18 | year=1968 | pages=400–443}}</ref> On the western side of the Atlantic, the slate pencil urchin has been found as far north as [[Cape Hatteras]], [[North Carolina]]<ref name=Cerame-vivas1966>{{cite journal |author1=Cerame-Vivas, MJ |author2=Gray IE | title=The distributional pattern of benthic invertebrates of the continental shelf off North Carolina | journal=Ecology | volume=47 | year=1966 | pages=260–270 | doi=10.2307/1933773 | jstor=1933773 | issue=2 | publisher=Ecological Society of America}}</ref> and as far south as [[Rio de Janeiro]].<ref name=Bernasconi1955>{{cite journal | author=Bernasconi I | title=Equinoideos y asteroideos de la coleccion del Instituto Oceanografico de la Universidad de San Pablo | journal=Boletim do Instituto Oceanográfico |location=São Paulo | volume=6 | year=1955 | pages=51–77 | doi=10.1590/s0373-55241955000100002}}</ref> In the Gulf of Mexico, populations have been reported at [[Scorpion Reef|Alacran Reef]], [[Campeche Bank]].<ref name=Kornicker1959>{{cite journal | vauthors=Kornicker LS, Bonet F, Cann R, Hoskin CM | last-author-amp=yes | title=Alacran Reef, Campeche Bank, Mexico | journal=Publications of the Institute of Marine Science | volume=6 | year=1959 | pages=1–22}}</ref> 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]].<ref name=Mortensen1928>{{Cite book| author=Mortensen, T | title=A monograph of the Echinoidea ''1'', Cidaroides | publisher=C.A. Reitzel | location=Copenhagen | year=1928 | pages=551}}</ref>
''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.<ref>{{cite journal |last1=Sciberras |first1=M. |last2=Schembri |first2=P.J. |year=2007 |title=A critical review of records of alien marine species from the Maltese Islands and surrounding waters (Central Mediterranean) |journal=Mediterranean Marine Science |volume=8 |issue=1 |pages= 41–66 |doi=10.12681/mms.162}}</ref>