It is well-known to geologists, that between those two great systems, of rocks the Silurian and Old Red Sandstone, there occurs an intermediate series of relatively small development, which, as it partakes of the lithologieal and palæontological characters of both has been well called “Transition-beds.” Transition-beds with contained Bone-beds .—That part of these beds which immediately overlies the Upper Ludlow Bock is composed of soft argillaceous shales; and that which immediately underlies the Old Bed, of a soft, yellow, fine-grained sandstone—the Downton Sandstone. Just below the Downton Sandstone, and therefore in the lowest part of these transition-strata, appears that remarkable animals-deposit called the “Ludlow Bone-bed”; and just above the Downton Sandstone, standing indeed within the threshold of the Old Red, another animal-deposit occurs, rarely, however, as an isolated conglomeration of organic remains as in the bone-bed, but most commonly having these more or less freely diffused throughout argillaceous and are naceous strata, or a gritty calcareous conglomerate which often becomes a compact bluish limestone. Thus, to speak generally, we have a lower bone-bed more appertaining to the Silurian system than to the Old Red; and an upper, more diffuse one, much more closely associated with the Old Red than with the Silurian Bocks. Both have their types at Ludlow,—the former in Ludford Lane and the north-eastern slopes of Whiteliffe; the latter in the strata exposed on the south bank of the Teme, opposite to the Gas-works and Paper-mill.