Selsam and Hunt's twelfth First Look begins with several ways in which sharks are different from other fish. Most notably, their skeletons are made of cartilage, not bone, and they give birth to live baby sharks instead of laying eggs; but the authors also point to less spectacular differences in scales, gills, tail fins, and mouth position. Then come the differences among sharks--in size, shape, teeth, fins, tail, and so on. And that's it. This latest lesson in taxonomy follows the series' pedagogical pattern with illustrations of all the differences and invitations for readers to sort them out. Limited, but where the series has held up this could add a link to the chain.