The Aleutian province, the centre of which may be taken to be the Aleutian islands, shows great analogy with the Boreal province of the west, a considerable number of the shells being identical—a fact especially interesting when we consider that very few species are found common to both the south-eastern and south-western coasts of America.
The Californian province is very distinct from that of Panama; the most numerous genera found there, are Chiton, Acmæa, Fissurella, Trochus, and Purpura.
The marine shells of Panama are upwards of thirteen hundred; the region included stretches from the Gulf of California to Peru. For our knowledge of this province we are much indebted to the researches of Dr. P. P. Carpenter, who has catalogued six hundred and fifty-four species, as found at Mazattan.
The Peruvian province contains a long list of species, and extends from Callao to Valparaiso.
The Magellanic province includes the extreme south of America and the Falkland Islands. Many genera, the species of which are usually small, here reach an enormous size, and afford, in many cases, the chief animal food consumed by the quadrupeds and human population of that wild and desolate coast.
The Patagonian province extends from St. Catharina to Point Melo on the east coast.
The number of species found also in the Falkland Islands is very small; but a large number are identical with Brazilian species; yet the majority are peculiar.
The Caribbean province extends from Brazil to the West Indies, and includes, also, the northern coast of South America and the Gulf of Mexico; a total of fifteen hundred species is enumerated by Professor Adams as belonging to the province.
The Transatlantic province, or that on the coast of the United States, does not afford a large number of species, only two hundred and thirty being known; of these, only fifteen are found in Europe.
The study of the terrestrial and fresh-water mollusca affords even better grounds for their division into provinces; but we shall not enter into it here, as it belongs to the Land World.