200 



UPPER LUDLOW ROCK. 



The strata above described compose the highest stage of the Upper Ludlow Rocks, 

 which member, while it contains a few of the most common Testacea of the subdivision, 

 is specially characterized by the abundance of remains of fishes, which are not rigidly 

 confined to the " bone bed ", but are occasionally found in other layers both above and 

 below it. 



The second stage or central mass of the Upper Ludlow Rock, is made up of strata 

 containing less sand and more calcareous matter than the overlying beds, mixed up 

 with the argillaceous paste ; and though used for building, they are, from the prevalence 

 of the argillaceous matter, generally prone to decomposition. When, however, used im- 

 mediately after extraction from the quarry, and laid horizontally, or in the direction of 

 the lamina?, these stones are tolerably durable, particularly when calcareous matter 

 prevails, some of them being even impure limestones. Though they do not furnish 

 flagstones, yet they are uniformly thin-bedded, the best stone when quarried never ex- 

 ceeding eight inches in thickness. (These strata appear in the foreground of the drawing 

 by Lady Harriet Clive, prefixed to this chapter, and the castle of Ludlow stands upon 

 them.) 



The surface of the beds is sometimes covered by wavy undulating ridges and furrows, 

 which are occasionally crossed by little raised tortuous bands. The ridges and furrows 

 are supposed to be due to the rippling action of waves, when the bed formed the surface- 

 bottom of the sea, and while the sediment was soft. The smaller transverse bands so 

 much resemble the marks made by animals which live at present in sandy shores, as to 

 induce the belief that many of the marks on these ancient rocks may have had a similar 

 origin. It is chiefly in this portion of the Upper Ludlow Rock that the best testaceous 

 and crustaceous remains are found, usually preserving all the sharpness of their form, 

 and frequently exhibiting the remains of the original shell. Besides the Leptana lata, 

 Cypricardia amygdalina, Orbicula rugata, and Avicula lineata, already mentioned as 

 occurring in the superior strata, these beds contain also many other shells, of which the 

 Orthis orbicularis and O. lunata PI. 5. figs. 15 and 16, Terebratula Nucula fig. 8, are the 

 most characteristic. We here see, and in abundance, the very peculiar form Serpuloides? 

 longissima PI. 5. fig. 1, often extending itself in segments of large circles ; and also two 

 species of the Homalonotus, that singular genus of crustaceans, hitherto noticed only 

 in the Ludlow formation, Homalonotus Knightii (Konig) and H. Ludensis nobis PI. 7. 

 figs. 1, 2, 3 and 4. Orthoceratites are abundant, particularly Orthoceras striatum PI. 5. 

 fig. 27. Some beds contain a small species of Turbo (T. corallii), so named because it 

 is frequently invested by a small coral (Favosites fibrosa, Goldfuss). I shall show in a 

 subsequent chapter to what great distances this shell and Turbo carinatus fig. 28. are 

 found associated with the same coralline envelope. 



The third or lowest stage of the Upper Ludlow Rock is distinguished from the over- 

 lying mass in being more argillaceous, less micaceous, and by occasionally running into 

 large spheroidal concretionary forms. Being very slightly coherent and easily decom- 



