species, were found abundantly for a few hundred feet up the creek.
At outlet of the lake, in a seepage pool just below the dam, were great numbers of Limnaea, alive, mingled with dead shells of a large Physa, but I could find none of the live Physas. The lake is formed by a dam thrown across the South Platte River shortly below the mouth of the stream which runs past Florissant. At the upper end are forming just such beds of fine mud as compose some portion of the Florissant lake beds. The beds were very much cracked, many of the cracks being an inch or two wide and nearly a foot deep, dividing the mud into blocks from a few inches to 3 feet across. The waters of the South Platte flow through Granite Canyon
