Echinodes (ekinoʻdez)

[NL. (Le Conte, 1869), ech i no glo al (e-ki-no-glos'al), a. and n. [ II. n. A member of the Ech i no glo a . hedgehog, sea-urchin, + είδος , form. Cf. Echi echinoid (e-ki'noid), a. and n. [ ἐχῖνος , α nodes.] I. a. 1. Having the form or appearance of a sea-urchin: in entomology, applied to certain insect-eggs which are shaped like an echinus, and covered with crowded deep pits.-2. Pertaining to the Ech i no idea. II. n. In zoöl ., one of the Ech i no idea . The spheroidal echinoids , in reality, depart further from the general plan and from the embryonic form than the elongated spatangoids do. Huxley , Lay Sermons, p. 223. Ech i no idea (ek-i-noi'de-ä), n. pl . [NL., Echi nus + -oidea .] ea . ] A cla of the phylum or subkingdom Echinoderm at a; the sea-urchins or sea-eggs. They have a rounded, depre ed (not elongated) form, sub spherical, cordiform, or discoid, inclosed in a test or shell composed of many calcareous plates closely and usually immovably connected, studded with tubercles and bearing movable spines, and perforated in some places for the emi ion of tube-feet; an oral and anal orifice always present, a convoluted intestine, a water-vascular system, a blood-vascular system, and sometimes respira tory as well as ambulatory appendages. The perforated plates are the ambulacra, alternating with imperforate interambulacral plates; there are usually five pairs of each. The anus is dorsal or superior, the mouth ventral or inferior; the latter in many forms has a complicated internal skeleton. The general arrangement of parts is radiate or act i nom eric, with meridional divisions of parts; but bilater ality is recognizable in many adults, and perfectly expre ed in the larval forms. The Ech i no idea are divisible into Re gularia , Des most ich a , or Endocyclica , containing the ordinary symmetrically globose forms, as Cidaris , Echinus , and Echinometra ; and the Irregular i a , Pet a lost ich a , or Exocy clica , containing the cake-urchins and heart-urchins, or the clype astroids and spatangoids (respectively sometimes erected into the orders Clypeastrida and Spatangida ); together with the Paleozoic echinoids, which in some systems constitute a third order, Palæchino idea. Also Echinoid a. IMG:content-0190.png:[merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small] a, mouth; a', gullet; d, teeth; c, lips; d, alveoli; e, falces: auricular iæ; g, retractor, and 4, protractor, muscles of Aristotle's lantern; i, madreporic canal, circular ambulacral ve el; 7, Polian vesicle; m, n, o, o, ambulacral ve els; P. 1, pedal vesicles; 9. 9, pedicels; ", ", spines; s, tubercle; s, tubercle to which a spine is articulated; t, t, pedicel lariæ; u, anus; v, madreporic tubercle; x, ocular spot.