This name is a synonym of Crataegus rivularis Nutt. ex Torr. & A.Gray.
The record derives from RJP
(data supplied on 2011-10-18)
which reports it as a synonym (record 18688) with original publication details: ; 1873-1874 137 1874.
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 rivularis in version 1 of The Plant List.