Page:Geology and Mineralogy considered with reference to Natural Theology, 1837, volume 1.djvu/217

 Rh on putrid vegetables and animal substances at the bottom; hence they have constant occasion to keep their bodies in the same inclined position as the extinct fossil Fishes, whose feeble brush-like teeth show that they also fed on soft substances in similar situations.

The Sharks employ their tail in another peculiar manner, to turn their body in order to bring the mouth, which is placed downwards beneath the head, into contact with their prey. We find an important provision in every animal to give a position of ease and activity to the head during the operation of feeding.

The Fishes of the Zechstein at Mansfeld and Eisleben have been long known, and are common in all collections; figures of many species are given by M. Agassiz. Examples of the Fishes of the Magnesian limestone of the north of England, are described and figured by Professor Sedgwick, in the Geol. Trans(of London, (2d Series, Vol. iii. p. 117, and Pl. 8, 9, 10.) He states in this paper (p. 99,) that the occurrence of certain Corals and Encrinites, and several species of Producta, Arca, Terebratula, Spirifier, &c. shows that the Magnesian limestone is more nearly allied in its