Page:Geology and Mineralogy considered with reference to Natural Theology, 1837, volume 1.djvu/223

 Rh family, Hybodonts, beginning with the Muschel-kalk, and perhaps with the Coal formation, prevails throughout the Oolite series, and ceases at the commencement of the Chalk. The third family of "Squaloids," or true Sharks, commences with the Cretaceous formation, and extends through the Tertiary strata into the actual creation.