Fossil worm casts

I've had a frustrating time today, trying to get another cactus spine shot. One of the main problems is that it is very hard to isolate one of a few spines without getting others that cross over and get in the way. Another thing I've been wanting to do is to photograph the grain of our new cedar cladding, but the light just isn't right this evening.

So feeling right out of ideas, I took the camera back to the spare bedroom where I keep it, and saw this piece of rock on the window cill. I put it on a wicker-seated chair, and photographed it with the light through the window. I found I got better definition using a diffuser. The fossils are worm casts, and the piece of rock was collected by my brother years ago. I have no idea where it comes from.