This name is a synonym of Crataegus chrysocarpa var. phoenicea E.J.Palmer.
The record derives from RJP
(data supplied on 2011-10-18)
which reports it as a synonym (record 7597) with original publication details: ; 1784 285 1784.
This name record (from RJP) was not included in version 1 of The Plant List. It is possible the same name was included from a different data source, to check this you can search for Mespilus rotundifolia in version 1 of The Plant List.