Substitute Saido Berahino's first-half strike, his second in the Premier League, handed the hosts the advantage and Gareth McAuley sealed the result seven minutes from time.
Palace, who saw manager Ian Holloway resign on October 23, remain rooted to the foot of the table under the guidance of caretaker boss Keith Millen.
It proved to be the Algeria international's last meaningful input as he was carried off on a stretcher following a collision with Myhill less than 10 minutes later.
On for the injured Billy Jones only 13 minutes earlier, the 20-year-old converted from Stephane Sessegnon's pass a minute before the break, finding the bottom corner to take his tally for the season to six in all competitions.
The home side came out with the same vigour in the second half and saw a chance to double their advantage go amiss in the 51st minute as Morgan Amalfitano's dangerous ball narrowly eluded Sessegnon and Shane Long.
Their increasingly desperate efforts ended up being in vein come the 83rd minute, though, as McAuley jumped highest to head a corner past Julian Speroni and put the result beyond doubt.
