Maslamah bin Abdullah bin Urwa is a narrator who is found in Tabaqat al-Kubra 2/271 here:-
A similar narrator with a slightly different name is also mentioned in Sunan Abu Dawud. His name is Maslama bin Abdullah Juhani. He can be found here:-
But the main question is: are these both narrators (Maslama bin Adullah bin Urwa and Maslama bin Abdullah Juhani) the same person/narrator?