I had a request to post pictures of the type of glass sponge fossils that can be found at the site I visited yesterday. Here are the two partial specimens I found there 2 weeks ago. In one shot I cobbed the two specimens together to represent what a complete specimen would look like. The pencil is for scale. The window screen like impressions in the rock are all that remains of the sponge. In life these structures were composed of a fibrous silicious material that somewhat resembled the mantle used for a Coleman camping lantern. Like a mesh. The sponge was rooted in the ocean floor. In life it drew food particles in the water in through the pores in the side known as ostia and expelled water through an opening at the top known as the osculum.