How to declare a structure?

I define an area of memory that in 'non-volatile' so it doesn't get cleared on powerup. I do this is a module called memmap.asm like this:
MyData DS 512 ;Located at 0x801C

In another module, I want to declare an array of structures starting at the address of MyData. I tried this:
struct tagData
{
BYTE Num1[32];
BYTE Num2[32];
};

struct tagData xdata MyArray[8] _at_ 0x801C

But this doesn't complile. What's wrong?

Thanks for any suggestions,
RickL