Recently, fossil land mammals have been recorded in the James Ross Island area, east of the Antarctic Peninsula, from the marine middle-late Eocene strata of Seymour Island. These include two endemic species of polydolopid marsupial: Antarctodolops dailyi Woodburne & Zinsmeister 1984, and Eurydolops seymourensis Case, Woodburne & Chaney 1988, and three partly determinate placentals identified as a tardigrade edentate, a sparnotheriodontid litoptern and a trigonostylopid astrapothere (Bond et al. 1989). The marsupials are represented by fragmentary jaw and complete dental material, the litoptern and astrapothere only by tooth fragments. All are recorded from Unit TELM 5 of the La Meseta Formation (Sadler 1988), the two ungulates at a lower level than the rest. The subject of the present note is a second tooth fragment from Seymour Island identified as an astrapothere. It is worth recording because such mammal remains are rare and it is from TELM 4, the unit below that yielding the other land mammals.