This name is a synonym of Crataegus pallasii Griseb..
The record derives from RJP
(data supplied on 2011-10-18)
which reports it as a synonym (record 2830) with original publication details: Flora rossica Flora rossica; 1784 26, t.12 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 Crataegus monogyna in version 1 of The Plant List.