passing a Vector3 List to a Vector3[]

I want to assign a list of Vector3s

var newVertices = new List.<Vector3>();

to - apparently - a Vector3[]

newMesh.vertices;

that doesn't take it with simple

newMesh.vertices = newVertices;

I tried

newVertices.ToArray(newMesh.vertices);

but the error shows "destination array was not long enough".

How do I assign a list type of array to an [] type of array?

Thought it was supposed to be more compatibile.

newMesh.vertices = newVertices.ToArray();