This name is a synonym of Crataegus mollis (Torr. & A.Gray) Scheele.
The record derives from RJP
(data supplied on 2011-10-18)
which reports it as a synonym (record 5323) with original publication details: Trees and shrubs Trees and shrubs; 1902 243 1913.
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 Crataegus placens in version 1 of The Plant List.