. The ancient life-history of the earth; a comprehensive outline of the principles and leading facts of palæontological science. Paleontology. Fig. 165.—Jurassic Brachiopods. a, Lepta-nn Linsska, enlarged, the small cross below the figure indicating the true size of the shell—Lias; b, Spb'ifera rostrata. Lias ; r. Terebratnla qnadrijida. Lias ; d, d', RhyncJwiiella vnriaiis, Fuller's Earth and Kello- way Rock ; e, Terebratnla sphcpj-aidalis, Inferior Oolite ;/, Terebratnla digona, Brad- ford Clay, Forest-marble, and Great Oolite. (After Davidson \ far the greater portion of the whole formation
. The ancient life-history of the earth; a comprehensive outline of the principles and leading facts of palæontological science. Paleontology. Fig. 165.—Jurassic Brachiopods. a, Lepta-nn Linsska, enlarged, the small cross below the figure indicating the true size of the shell—Lias; b, Spb'ifera rostrata. Lias ; r. Terebratnla qnadrijida. Lias ; d, d', RhyncJwiiella vnriaiis, Fuller's Earth and Kello- way Rock ; e, Terebratnla sphcpj-aidalis, Inferior Oolite ;/, Terebratnla digona, Brad- ford Clay, Forest-marble, and Great Oolite. (After Davidson \ far the greater portion of the whole formation, the Bivalves are of course marine, and belong to such genera as Tiigonia, Lima, F/ioIadomya, Cardima, Avicula, Hippopodium, &c. ; but in the Purbeck beds, at the summit of the series, we find bands of Oysters alternating with strata containing fresh-water or brackish-water Bivalves, such as Cyrence and CorbiilcB. The predominant Bivalves of the Jurassic, however, are the Oysters, which occur under many forms, and often in vast numbers, particular species being commonly restricted to particular horizons. Thus of the true Oysters, Ostrea distorta is char- acteristic of the Purbeck series, where it forms a bed twelve feet in thickness, known locally as the " Cinder-bed ;" Osfrca expansa abounds in the Portland beds; Ostrea deltoidea is characteristic of the Kimmeridge clay ; Ostrea gregaria pre- dominates in the Coral-rag ; Ostrea acuminata characterises the small group of the Fuller's Earth ; whilst the plaited Ostrea Marsha (fig. 166) is a common shell in the Lower and Middle Oolites. Besides the more typical Oysters, the Oolitic rocks abound in examples of the singularly unsymmetrical forms. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Nicholson, Henry Alleyne, 1844-1899. Edinburgh, L
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Keywords: ., bookaut, bookcentury1800, bookdecade1870, booksubjectpaleontology
