You can search on a name and you will find a number of Devonshires in the parish, which also contains St. Ewe - there are christenings, marriages, burials and cemetery inscriptions - all very interesting. I think you will find your Richard mentioned there.
I am interested in Commander John Ferris Devonshire, RN who was with Nelson at the Battle of Copenhagen and subsequently beacame a Justice of the Cormwall Quarter Sessions Court in Turo.
My Devonshire link is through my GGG Grandmother Thamzin (or Thomzin or Thomasin) Devonshire who married Lt. George Thomas Wingate, RN in 1801. I have information that she was a resident of Plymouth Dock at the time of their marriage in Portsea, Hampshire.