Hiya
there certainly isn't such a parish on the latest OS map and as TCL says, if it is a place u are looking for for reaserch purposes the place name may well have been transcribed incorrectly.
I have looked at the Parish Map of Bedfordshire for 1881 and there is no parish called Dereham then .
http://i2.tinypic.com/23qxg9d.jpg
If this is a place name from a family history source, what is the source? if it is the enumerators written place of birth it should also give a county, sorry if it is not FH related.
dotty
xxxx