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NELLIDAE, TEREBRATULIDAE

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Originally appearing in Volume V04, Page 366 of the 1911 Encyclopedia Britannica.
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NELLIDAE, TEREBRATULIDAE ,STRINGOCEPHALIDAE, MEGALANTERIDAE, TEREBRATELLIDAE, ATRYPIDAE, SPIRIFERIDAE, See also:ATHY RIDAE. Affenities.—Little See also:light has been thrown on the See also:affinities of the See also:Brachiopoda by See also:recent See also:research, though See also:speculation has not been wanting. Brachiopods have been at various times placed with the See also:Mollusca, the See also:Chaetopoda, the See also:Chaetognatha, the See also:Phoronidea, the See also:Polyzoa, the Hemichordata, and the Urochordata. None of these alliances has See also:borne See also:close See also:scrutiny. The See also:suggestion to See also:place Brachiopods with the Polyzoa, Phoronis, Rhabdopleura and Cephalodiscus, Iii the Phylum Podaxonia made in Ency. Brit. (vol. xix, ninth edition, pp. 440-441) has not met with See also:acceptance, and until we have a See also:fuller See also:account of the See also:embryology of some one See also:form, preferably an In-articulate, it is wiser to regard the See also:group as a very isolated one. It may, however, be pointed out that Brachiopods seem to belong to that class of See also:animal which commences See also:life as a larva with three segments, and that tri-segmented larvae have been found now in several of the larger See also:groups. See also:Distribution.—Brachiopods first appear in the See also:Lower See also:Cambrian, and reached their highest development in the See also:Silurian, from which upwards of 2000 See also:species are known, and were nearly as numerous in the Devonian See also:period ; at See also:present they are represented by some 140 recent species. The following have been found in the See also:British See also:area, as defined by A. M.

See also:

Norman, Terebratulina caput-serpentis L., Terebratula (Gwynia) capsula Jeff., Magellania (Macandrevia) cranium Miill.,M. septigera Loven,Terebratella spitzbergenensis See also:Day., Megathyris decollata Chemn., Cistella cistellula S. See also:Wood, Cryptopora See also:gnomon Jeff., Rhynchonella (Hemithyris) psittacea Gmel., Crania anomala See also:Mull., and Discinisca atlantica See also:King. About one-See also:half the 120 existing species are found above the too-fathoms See also:line. Below 150 fathoms they are rare, but a few such as Terebratulina wyvillei are found down to 2000 fathoms. Lingula is essentially a very shallow See also:water form. As a See also:rule the genera of the See also:northern hemisphere differ from those of the See also:southern. A large number of specimens of a species are usually found together, since their only mode of spreading is during the ciliated larval See also:stage, which althoughyit swims vigorously can only See also:cover a few millimetres an See also:hour; still it may be carried some little distance by currents. Undue stress is often laid on the fact that Lingula has come down to us apparently unchanged since Cambrian times, whilst Crania, and forms very closely resembling Discina and Rhynchonella,, are found from the Ordovician strata onwards. The former statement is, however, true of animals from other classes at least as highly organized as Brachiopods, e.g. the Gasteropod Capulus, whilst most of the invertebrate classes were represented in the Ordovician by forms which do See also:net differ from their existing representatives in any important respect. A full bibliography of Brachiopoda (recent and fossil) is to be found in See also:Davidson's Monograph of British Fossil Brachiopods, See also:Pal. See also:Soc. Mon. vi., 1886.

The Monograph on Recent Brachiopoda, by the same author, Tr. Linn. Soc. See also:

London, Zool. See also:ser. ii. vol. iv., 1886-1888, must on no account be omitted. (A. E.

End of Article: NELLIDAE, TEREBRATULIDAE

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