There are also some sites that are accessible by boat and here's one of these cheniers. We trench these cheniers and collect the specimens. Most of the material that you're looking at in this ridge is shell material, and 99.9 percent of the material in this ridge belongs to a single species of bivalves and that species is Mulinia coloradoensis, a very little known bivalve. Mulinia coloradoensis, however, was so abundant in the gulf in previous years, that it's lead one of our colleagues to describe the scene as "billions and billions of shells." And it literally is. You can stand at some parts of planes and you see nothing but shells of Mulinia as far as the eye can see.

However, Mulinia was thought to be extinct since the 1960's until a fisherman brought us some pickled specimens in 1997. We were just amazed that he found live specimens. We've since located the population. It's located just a bit north of this region which is the furthest, the northern most expanse of the gulf, which is at the very mouth, or former mouth, of the river and there's a very small population there. That's very interesting and disturbing because Mulinia, as I said, was overwhelmingly the most abundant macro invertebrate in the northern gulf and it extended further than 100 kilometers to the south and now you find it within a kilometer at the edge of the gulf.

Another species that we collect here, which is the second most abundant species, I guess we know 2 percent of what we find there, is a bivalve called Chione fluctifraga. We use Chione for our reconstructions for two reasons: it's a very nice robust shell that we can sample easily and Chione, unlike Mullinia, is still very abundant today.

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