Madagascar is the home of one or two other species of fruit-bat, two species of the horseshoe-bats (_Rhinolo-phidæ_), seven species of the _Vespertilionidæ_ or true bats, and three species of the _Emballonuridæ_ or thick-legged bats; no doubt there are still many species undescribed, and until much more minute investigation is made of the fauna of the island, the crepuscular and nocturnal habits of these animals will always make it difficult to learn much about their peculiarities. The morning’s voyage brought us in several places along low sections of stratified sandstone rock, looking like ruined walls, some courses being deeply honeycombed by the action of the water, while others, of harder material, were smooth, like newly laid masonry. It was clear that we had left behind us, in the upper highland, the crystalline rocks, the granites and gneisses and the like, and were in a region of Secondary strata, like the oolites of our own country. Subsequent examination by many observers has confirmed this fact, and shown that an extensive series of Jurassic and Cretaceous rocks occupies a great portion of the western low land, from north to south of the island. These plains must have formerly been a portion of a wider Mozambique Channel than now exists to separate Madagascar from Africa. In certain shales which occur among the Secondary strata of the western plains, Belemnites are so numerous that the Sàkalàva used them as rifle balls; while many species of ammonites are formed, some being a foot in diameter. [Sidenote: THE SÀKALÀVA]