270 PHYLUM ECHINODERMATA, 



Class CRINOIDEA* 



Brachiate Echinoderms attached during the whole or part of life 

 by the aboral apex of the body. The arms are usually provided with 

 pinnules and branched, the tube-feet are tentacle-like and with- 

 out ampullae, the water-pore is always multiple, and the anus is 

 interradially placed on the oral surface. 



All living Crinoids are, so far as is known, attached, either in 

 the young state only (Comatulids, Thaumatocrinus] or through- 

 out life, by a jointed stalk proceeding from the apical point of 

 the body. The body consists of a calyx or disc, and of radial 

 branched prolongations of the disc the arms. The branches 

 of the arms may be all alike, or some of them, known as pin- 

 nules, may differ in structure from the others. In the natural 

 position of the animal the abactinal (dorsal of adult) surface is 

 turned towards the substratum, to which indeed it is, as already 

 stated, generally fixed by a stalk, while the actinal (ventral of 

 adult) surface is directed upwards. 



The actinal surface of the calyx is called the calyx-cover 

 (tegmen calycis] and bears, usually | in its centre, the mouth, 

 from which radiate towards the periphery on the calyx-cover 

 the ambulacral grooves (food grooves). The portions of the 



* J. S. Miller, A Natural History of the Crinoidea or Lily -shaped Animals, 

 Bristol, 1821. J. V. Thompson, " Sur le Pentacrinus Europaeus, Vital de 

 jeunesse du genre de Comatula," L'Institut, 1835. Id., " Memoir on the 

 Starfish of the genus Comatula," Edinburgh New Phil. Journ., 20, 1836. 

 J. Miiller, " Ueu d. Bau. v. Pentacrinus caput medusae," Abhand. d. 

 Berlin Akad., 1841. Id. " Ue^b. d. Gattung Comatula u. ihre Arten," 

 ibid., 1847. W. B. Carpenter, Researches on the Structure, Physiology 

 and Development of Antedon rosaceus, Phil. Trans., 156. H. Ludwig, 

 Crinoiden, Z.f.w.Z., 1877, 28, p. 257 ; and 29, p. 47. P. H. Carpenter, 

 " Report on the Crinoidea," Challenger Reports, I, " The stalked 

 Crinoids," 1884, and II, "The Comatulae," 1888. M. Neumayr, Die 

 Stamme des Thierreiches, 1, 1889. C. Wachsmuth and F. Springer, 

 " Revision of the Palaeocrinoidea," Proc. Acad. Nat. Sci. Philadelphia, 

 1879, 1881, 1885. Id., " Discovery of the ventral Structure of Taxo- 

 crinus and Haplocrinus, etc." Ibid., 1889. Id. " The perisomic plates of 

 Crinoids," Ibid. 1890. Id., North American Camerata, Mem. Mus. 

 Harvard, 20 and 21, 1897. E. Perrier, "Memoire sur 1'Organisation et le 

 developpement de la Comatule de la Mediterranee," Nouv. Archives Mus. 

 Hist. Nat. Paris, 1886-92. H. Bury, " The early stages in the development 

 of Antedon rosacea," Phil. Trans. 179, 1888. O Seeliger, " Studien zur 

 Entwick. der Crinoiden," Zool. Jahrb., Abth. f. Anat. 6, 1892. H. Ludwig, 

 loc. cit. F. A. Bather, " British fossil Crinoids," a series of papers in Ann. 

 and Mag. Nat. Hist. (6), 5, 1890. Id., The Crinoidea of Gotland, Pt. 1. 

 Kongl. Svenska Vetenskaps-Akad. Hand., 25, 1893. Id., Crinoidea, in 

 Lankester's Zoology, Pt. 3, 1900 (Literature given). Reichensperger, 

 ** Anatomie von Pentacrinus," Z.f.w.Z., 80, 1905, p. 22. 



| In Actinometra the mouth is excentric, and the anus is nearly central. 



