saddletank

English Wikipedia has an article on:

saddle tank

Wikipedia

From saddle +‎ tank.

saddletank (plural saddletanks)

1. (rail transport) A style of tank locomotive in which the water tank sits on top of the boiler like a saddle.
   • 1959 October, Norman Jones, “The Manchester Ship Canal Railway”, in Trains Illustrated, page 488:

     The smart little locomotives, mostly 0-6-0 saddletanks, which are always busy shunting traffic amongst the vast dockside warehouses, belong to the Manchester Ship Canal Railway, a line of considerable importance.

2. (naval architecture) An early style of ballast tank submarine in which the tank sits on top like a saddle.

• saddle tank