. Elements of geology, or, The ancient changes of the earth and its inhabitants as illustrated by geological monuments. Geology. Ch. xxvn.] LINGULA FLAGS. 577 Lower Silurian forms, belong to the genera, Ogygia, Asapkus, and Ckeirurus; whereas those belonging to primordial types, or Bar rande's first fauna, as well as to the Lingula flags of Wales, comprise Conocoryphe* Olenus, several species, and Angelina. In the Upper Tremadoc slates are found Bellerophon, Orthoceras, and Cyrtoceras, all specifically distinct from Lower Silurian fossils of the same genera: the Pteropod Theca ranges throughou
. Elements of geology, or, The ancient changes of the earth and its inhabitants as illustrated by geological monuments. Geology. Ch. xxvn.] LINGULA FLAGS. 577 Lower Silurian forms, belong to the genera, Ogygia, Asapkus, and Ckeirurus; whereas those belonging to primordial types, or Bar rande's first fauna, as well as to the Lingula flags of Wales, comprise Conocoryphe* Olenus, several species, and Angelina. In the Upper Tremadoc slates are found Bellerophon, Orthoceras, and Cyrtoceras, all specifically distinct from Lower Silurian fossils of the same genera: the Pteropod Theca ranges throughout these slates; there are no Graptolites. The only Tremadoc species which, according to Salter, is not peculiar, is Lingula Davisii, which ranges from the top to the bottom of the formation, and links it with the zone next to be de- scribed. The Tremadoc slates .are very local, and seem to be con- fined to a small part of North Wales; and Prof. Ramsay supposes them to lie unconformably on the Lingula flags, and that a long inter- val of time elapsed between these formations. Lingula Flags.—Next below the Tremadoc slates in North Wales, lie micaceous flagstones and slates, in which, in 1846, Mr. E. Davis discovered the Lingula named after him, and from which was de- rived the name of Lingula In these flags and shales, other fossils were found by subsequent researches, which were observed to differ specifically from those of the Llandeilo beds, or the lowest por- tion of the Lower Silurian then palaeontologically known. Trilobites of the genera Olenus and Conocoryphe (for genus, see fig. 667), and other forms, which will soon be published by our Government Sur- vey, were detected; and (for genus, see fig. 666), another Fossils of the "Lingula Flags" or lowest Fossiliferous Rocks of Britain. Fig. 661. Fig. 662. Fig. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - col
Size: 1883px × 1328px
Photo credit: © Paul Fearn / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1860, booksubjectgeology, bookyear1868
