. The ancient life-history of the earth; a comprehensive outline of the principles and leading facts of palæontological science. Paleontology. 122 HISTORICAL PAL/EONTOLOGY. another. The arms are typically five in number; but they generally subdivide at least once, sometimes twice, and they. Fig. 62.—Upper Silurian Crinoids. a, Calyx and arms oi Eiccalyptocrbnis polydacty- his, Wenlock Limestone ; b, Icht]iyoc7-i7ncs icsz'is, Niagara Limestone, America ; c, Taxocrimis tiiberczilatics, Wenlock Limestone. (After IM'Coy and Hall.) are furnished with similar but more slender lateral branches or &qu
. The ancient life-history of the earth; a comprehensive outline of the principles and leading facts of palæontological science. Paleontology. 122 HISTORICAL PAL/EONTOLOGY. another. The arms are typically five in number; but they generally subdivide at least once, sometimes twice, and they. Fig. 62.—Upper Silurian Crinoids. a, Calyx and arms oi Eiccalyptocrbnis polydacty- his, Wenlock Limestone ; b, Icht]iyoc7-i7ncs icsz'is, Niagara Limestone, America ; c, Taxocrimis tiiberczilatics, Wenlock Limestone. (After IM'Coy and Hall.) are furnished with similar but more slender lateral branches or " pinnules," thus giving rise to a crown of delicate feathery plumes. The "column" is the stem by which the animal is attached permanently to the bottom of the sea; and it is com- posed of numerous separate plates, so jointed together that whilst the amount of movement between any two pieces must be very limited, the entire column acquires more or less flexi- bility, allowing the organism as a whole to wave backwards and forwards on its stalk. Into the exquisite minutics. of structure by which the innumerable parts entering into the composition of a single Crinoid are adapted for their proper purposes in the economy of the animal, it is impossible to enter here. No period, as before said, has yielded examples of greater beauty than the Upper Silurian, the principal genera represented being Cvatkocrifius, Platycrinus^ Marsupiocriims, Taxocrinus, Eucalyptoainus, Ichthyocrinus^ Mariacri?ius, Pcricc/iocrhius, Glyptocrinus^ Crotalocrimis^ and Edriocriniis. The tracks and burrows of Anndides are as abundant in the Upper Silurian strata as in older deposits, and have just as commonly been regarded as plants. The most abundant forms are the cyhndrical, twisted bodies (Planolites), which are. 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
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Keywords: ., bookaut, bookcentury1800, bookdecade1870, booksubjectpaleontology
