Note 93 — Chapter III

This argument of Testa has been strengthened of late years by the discovery that dealers in shells had long been in the habit of selling Mediterranean species as shells of more southern and distant latitudes, for the sake of enhancing their price. It appears, moreover, from several hundred experiments made by that distinguished hydrographer, Capt. Smith, on the water within eight fathoms of the surface, that the temperature of the Mediterranean is on an average 3½° of Fahrenheit higher than the western part of the Atlantic ocean; an important fact, which in some degree may help to explain why many species are common to tropical latitudes and to the Mediterranean.