peristome
(ˈpɛrɪstəʊm)
Also in L. forms peˈristoma (pl. -ata), periˈstomium (pl. -ia).
[= F. péristome (18..), ad. mod.L. peristoma (Hedwig 1782), f. Gr. περί around + στόµα mouth; altered (by Ehrhart 1787) to peristomium, after pericarpium, etc.]
1. Bot. The fringe of small teeth around the mouth of the capsule or sporangium in mosses.
| 1796 Withering Brit. Plants (ed. 3) I. 73 Peristoma, the fringe at the mouth of the Capsule of Mosses. 1818 Hooker & Taylor Musc. Brit. Introd. 4 The absence or presence of the fringe of the Peristome which Hedwig employed to so much advantage. 1830 Lindley Nat. Syst. Bot. 320 One or more rows of cellular rigid processes, called collectively the peristomium, and separately teeth. 1875 Bennett & Dyer Sachs' Bot. 331 We must now examine somewhat more closely the origin of the Peristome. |
2. Zool. a. The margin of the aperture of the shell of a mollusc.
b. Any special structure or set of parts around the mouth or oral opening in various invertebrates, as insects, crustacea, hydrozoa, infusoria; in echinoderms, the part of the body-wall surrounding the mouth (
opp. to
periproct); in certain worms, as earthworms, the first true somite, situated behind the
prostomium or
præstomium, and bearing the mouth.
| a. 1851–6 Woodward Mollusca 101 The margin of the aperture is termed the peristome. 1870 Rolleston Anim. Life 47 The columella is seen in the angle..; its umbilicus is partly..concealed by the reflection over it of the peristome. |
| b. 1875 Huxley & Martin Elem. Biol. (1877) 93 (In Vorticellæ) α. The prominent everted rim (peristome). 1877 Huxley Anat. Inv. Anim. v. 232 (Chætopoda) The first somite, which contains the mouth, is the peristomium. Ibid. ix. 569 (Echinodermata) The ambulacral plates are continued on the peristome to the margins of the mouth. 1888 Rolleston & Jackson Anim. Life 781 (Hydrozoa Acraspeda) The mouth.. is situate in the centre of a disc or peristome of great mobility. 1896 Cambridge Nat. Hist. II. 481. |
Hence
periˈstomal,
periˈstomial adjs., surrounding the mouth, circumoral; pertaining to, of the nature of, or having a peristome.
| 1888 Rolleston & Jackson Anim. Life 547 Peristomal gills of some Echinoidea. 1900 Proc. Zool. Soc. 278 The peristomal plates..number in adults normally 9 in one row and 8 in the other row of the pair. 1870 Nicholson Man. Zool. 99 Between the mouth and the circumference of the disc is a flat space, without appendages of any kind, termed the ‘peristomial space’. 1881 Spruce in Jrnl. Bot. X. 18 Recklessly bandied about among peristomial genera. 1896 Cambridge Nat. Hist. II. 313 There are four long peristomial cirri on each side. Ibid. 185 The peristomial depression. |