Crossing the Isthmus and following the Pacific shore of the continent northward, we find a sandy open shore alternating with rocky beaches as far north as Acapulco. Along this coast there is to be found a great variety of corals, especially Sea-fans, growing on the rocks, but no reef. The Pocillopora, an Acalephian coral, the Pacific representative of the Millepore of Florida, is especially abundant. On the peninsula of Lower California we come again upon a rocky coast, with steep bluffs, extending into the sea. Within the Gulf of California are found, on its sandy coast, peculiar kinds of Sea-urchins, Spatangoids, and Clypeastroids, which occur nowhere else on this coast. From Cape St. Lucas up to the Straits of Fuca, with the exception of the large estuary forming the Bay of San Francisco, there are scarcely a couple of harbors of any consequence. The whole shore is most inhospitable, and the violent northwest winds in summer, and the southeast winds in winter, render it still more bleak and difficult of approach. In consequence of these conditions, the fauna is scanty along a great part of the shore; the best spots for collecting are the beaches, near the head of the peninsula, opposite the islands of Santa Barbara and San Diego, and that within the harbor of San Francisco. On the former, large Craw-fishes abound (Palinurus), akin to those of Florida, though specifically different from them. In the latter, the great amount of fresh water prevents the fauna from being exclusively marine; this harbor is, nevertheless, the great centre of the viviparous fishes, and contains also a large variety of peculiarly shaped Sculpins.