So I found this specimen by the river in san sebastian and according to https://www.jstor.org/stable/1301379?read-now=1&seq=5#page_scan_tab_contents it could be either Echinometra lucunter or belonging to Thylechinus. Both of these specimens (supposedly both specimens have only been found once in Puerto Rico) look alike so much according to my recent searches that im now more confused than ever. Any expert out there who can help?