structs and function-declaration

If I declare a couple of c-style structs like so:

struct TRIANGLE {
	float4 p[3];
struct GRIDCELL {
	float4 p[8];
	double val[8];

and then attempt to use an input/output variable of that type in a function, like this

int Polygonise(GRIDCELL grid, double isolevel, TRIANGLE *triangles) {
   int i, ntriang;
   int cubeindex;
   float4 vertlist[12];

I get an error about an expected ‘)’ character. I imagine this is just a syntax issue, but I can’t find anything in the documentation covering this exact scenario. The code I’m working on is a version of Paul Bourke’s Marching Cubes source, originally written in C.

Any tips much appreciated.