FOSSIL CRINOIDS. About 175 genera and 2000 species of fossil crinoids are known. They appear first as very simple forms in Ordovician rocks, and they increase rapidly. becoming important elements of the faunas in the Silurian, Devonian, and Carboniferous periods. In some regions they were exceedingly abundant, for their fossil re mains form great beds of limestone known as 'crinoidar or 'enerinal limestone,' which are found in formations of various ages. In the Silurian system alone, about 400 species, distributed among 70 genera, have been obtained from mostly three localities: the island of Gotland, the Wen lock of England, and the Niagara group of North America. Sonic of the more characteristic genera are Pisoerinus, Crotalocrinns, Calceocrinus, Calli erinus, and Euenlyptocrinns. In the Devonian system some localities have yielded gootl material. The Lower Carboniferous rocks of the upper Mississippi Valley are the most renowned sources of fossil crinoids. The shaly limestone beds at Burlington, Iowa, and Crawfordsville. lad., have furnished hosts of finely preserved specimens, which are to he seen in geological collections all over the world. The Mesozoic rocks of Europe, especially the Liassic and Jurassic. have fur nished some fine examples of Enerinus, Apio erinus, and the pentacrinids. but time rocks of this era in America hold only rare occurrences of members of this class. The only find of note—and that was one of great importance—was that of Vintacrinus in the Cretaceous chalk of western Kansas. The Tertiary rocks seem to be poor in fossil remains of this group.
Binuomurny. General descriptions of the class, and notes on the habits of the animals, can be found in: Agassiz. Three Cruises of the Blake,
vol. ii. (Boston and New York. 1888) Walther, Einleitung in die Geologic als Imistoriscbc Wissen schaft (Jena, 1893-94) : Neunmyr, Die Stiimme des Thicrreiches. vol. i. (Vienna and Prague, 1889) : Parker and Haswell, Textbook of Zoology, vol. i. (London and New York. 1897) ; Carpenter, "Report on the Crinoidea," in Challenger Reports, Zoology, vol. xi., No. 26, and vol. xxvi.. No. 60 (London, l884-88). For description of the fossil forms, consult: Zittel and Eastman. Textbook of Paleontology. vol. i. ( London and New York, 1900) : Bather. "The Crinoidea," in Lankester's Treatise on ZoOlogy, part ii. (London, 1900) ; Wachsmuth and Springer, "Revision of the Pahro erinoidea," Proceedings of the Academy of Natu ral Sciences at Philadelphia, for 1879, 1881,1885, and 1886; "North American Crinoidea Camerata," -Memoirs of the Museum of Comparative Zoology at Harvard College, vols. xx. and xxi. (Boston, 1897) ; Bather, "TheCrinoidea of Gotland."Kong liga Srenska Vetrnskap Akademiens Handlingar, vol. xxv. (Stockholm, 1892) : Lang and Bernard, Textbook of romparatire Anatomy, part ii. (Lon don and New York. 1890) : Weller. "The Paleon tology of the Niagaran Limestone in the Chicago Area. The Crinoidea," Bulletin No. ir.Of the Nat u ral History Surrey. Chicago Academy of Sciences (Chicago. 1900) : Bather. "On Vintaerinus: A :Morphological Study." Proceedings of the Zoologi cal Society of London. vol..1895 (London, 1896). See also articles on ECIIINODERINIATA ; CYSTO IDEA ; PENTREMITES.