Yes, there is a silly mid on, and a silly mid off. They are all I remember from my first cricket lesson, which attempted to introduce me to all the places a fielder could stand. Each potential position has a name covering the area of the pitch, to enable the captain to tell people where to go. There are more named positions than fielders, and many of them have names which seem strange to non-combatants - slips, gully, etc, though some are clearer. On and off refer to which side of the batter they are, rather like nearside and offside of a car, but I don't know which is which. The sillies are close to the batter, so could get a fast moving ball arriving very quickly.
I wish I'd been taught by having a mock up pitch and being asked to suggest where to put the fielders for a particular combination of bowler and batter. I'd only have had to learn a few names at a time, and I'd know why they were there.
New Scientist had an article once, comparing baseball pitching with cricket bowling, and explaining the physics of a baseball curving in flight - which I forget, but which is presumably related to swing in cricket.
What are all those signals in baseball about? In cricket, the signals are about what's just happened, not what's going to happen, so are easier to work out.
I have heard it said that cricket is a game between 24 men (teams and umpires) and the scorers. You wouldn't believe how fast it goes when you are filling in all the little boxes.
Penny