5. Ophiuroidea

Ophiuroidea. The "brittle-stars" are represented in the Silurian rocks by some anomalous genera, of which the best known is Protaster. In the Triassic, Oolitic, Cretaceous, and Tertiary rocks various genera of Ophiuroidea are known; some being extinct, whilst others still survive at the present day.

6. Echinoidea

Echinoidea. This order is represented in the Palaeozoic rocks by a single aberrant family; but it is numerously represented in the Mesozoic and Kainozoic periods.

Of the Palaeozoic Urchins or Perischoechinidae, the two most abundant genera are Archaeocidaris and Palaechinus, both of which are principally Carboniferous, though the latter occurs in the Upper Silurian. Melonites and O/igoporus are exclusively Carboniferous; and Lepidechinus and Eocidaris are principally so, though both commence their existence in the Devonian.

The Secondary and Tertiary Echinoidea resemble those now living in being composed of not more than twenty rows of calcareous plates. The Oolitic and Cretaceous rocks are especially rich in forms belonging to this order, many genera being peculiar; but the number of forms is too great to permit of any selection.

It may be mentioned, however, that the singular genus Echinothuria, with its flexible test, the predecessor of the living Asthenosoma and Phormosoma, is found in the Chalk.

7. Holothuroidea

Holothuroidea. This order, comprising, as it does, soft-bodied animals, has left but few traces of its existence in past time. The calcareous integumentary plates and spicules of Sea-cucumbers are, however, by no means absolutely unknown in the fossil condition, ranging from the Carboniferous onwards. The shield of Psolus has also been detected in Post-tertiary deposits in Bute.

Literature. General Works

1. "Klassen und Ordnungen des Thier-Reichs," vol. ii. 'Strahlenthiere.' Bronn. 1860.

2. "A History of British Star-fishes and other Animals of the Class Echinodermata." Edward Forbes. 1841.

3. "Grundriss der Vergleichenden Anatomic" Gegenbaur. 1874.

4. "Die Larven und Metamorphosen der Echinodermen." J. Muller.

'Abhandl. Berlin Akad.' 1848-55.

5. Article "Echinodermata." Sharpey. Todd's 'Cyclopaedia of Anatomy and Physiology.' 1839.

6. "Anatomie der Rohren-Holothurie," etc. Tiedemann. 1820.

7. "Morphologische Studien an Echinodermen." H. Ludwig. 'Zeitschr. f. Wiss. Zool.,'vols. xxviii.-xxxi.

8. "Beitrage zur Anatomie der Echinodermen." R. Teuscher. ' Jenaische Zeitschr.,' vol. x.

9. "Peculiarities in the Mode of Propagation of certain Echinoderms of the Southern Seas." Wyville Thomson. 'Journ. Linn. Soc.,' vol. xiii. 1876.

Echinoidea.

10. "Monographies d'Echinodermes vivants et fossiles." Louis Agassiz.

1838-41.

11. "Catalogue raisonne des families, des genres, et des especes de la classe des Echinodermes." Louis Agassiz and Desor. 1847.

12. "Revision of the Echini." Alexander Agassiz. 'Memoirs of the Museum of Comparative Zoology at Harvard,' vol. iii. 1872-74.

13. "Monograph of the British Fossil Echinodermata." Thomas Wright.

'Palseontographical Society.'

14. "Monograph of the Echinodermata of the British Tertiaries." Edward Forbes. ' Palaeontographical Society.'

15. "Paleontologie Francaise, Terrains Cretaces," torn. vi. and vii.

'Echinodermes.' A. D'Orbigny and G. Cotteau. 1856-57 and 1861-67.

16. "Synopsis des Echinides fossiles." E. Desor. 1855-59.

17. "Etudes sur les Echinoides." S. Loven. 1874.

18. "Recherches sur l'appareil circulatoire des Oursins." Perrier. 'Arch. de Zool. Exper. et Gen,' vol. iv. 1876. Asteroidea And Ophiuroidea.

19. "System der Asteriaden." Muller and Troschel. 1843.

20. "British Fossil Echinodermata." ' The Asteroidea.' Thomas Wright.

' Palaeontographical Society.'

21. "Ophiuridae and Astrophytidae." Theodore Lyman. 'Illustrated Catalogue of the Museum of Comparative Zoology at Harvard.' 1865.

22. "Ueber die Larven und die Metamorphosen der Ophiuren." J.

Midler. 'Abhandl. Berlin Akad.' 1846. (See also several of the works mentioned under the head of "General works." As regards the development of the Asteroids and Ophiuroids, the English student may consult Professor Huxley's "Report upon the Researches of Professor Muller into the Anatomy and Development of Echinoderms," in the 'Annals of Natural History,' ser. 2, vol. viii. 1851; or Packard's ' Life-Histories of Animals.') 23. "Beitrage zur Anatomie und Histologic der Asterien und Ophiuren." Lange. 'Morphologisches Jahrb.,' vol ii.

24. "Additamenta ad historian Ophiuridarum." Lutken. 1859.

25. "North American Star-fishes." A. Agassiz. 1877.

Crinoidea.

26. "A Natural History of the Crinoidea," etc. J.S.Miller. 1821.

27. "Memoir on the Pentacrinus Europaeus." J. V. Thompson. 1827.

28. "Ueber den Pentacrinus caput-Medusae." J. Muller. 1843.

29. "Recherches sur les Crinoides du terrain carbonifere de la Belgique."

De Koninck and Le Hon. 1854.

30. "Development of Comatula." Sir Wyville Thomson. 'Phil. Trans.'

'1865

31. "The Depths of the Sea." Sir Wyville Thomson. 1873.

32. "Notice of new living Crinoids belonging to the Apiocrinidae." Sir Wyville Thomson. 'Journ. Linn. Soc,' vol. xiii. 1876.

33. "On the Structure, Physiology, and Development of Antedon rosaceus." Dr W. B. Carpenter. ' Proc. Roy. Soc' 1876.

34. "Anatomy, Physiology, and Development of Comatula." Dr W. B.

Carpenter. 'Phil. Trans.' 1866.

35. "The Crinoidea of the Lower Silurian Rocks of Canada." E. Billings. 'Figures and Descriptions of Canadian Organic Remains,' Decade iv. 1859.

36. "Memoires pour servir a la connaissance des Crinoides vivants." M.

Sars. 1868. 37. "Anatomy of the Arms of Crinoids." 'Journ. Anat. and Phys.,' vols. x. and xi. P. H. Carpenter.

38. "Anatomy of Pentacrinus and Rhizocrinus." 'Journ. Anat. and Phys.,' vol. xii. P. H. Carpenter.

39. "On the Genus Actinometra." 'Trans. Linn. Soc' 1877. P. H.

Carpenter.

40. "On the Oral and Apical Systems of Echinoderms." 'Quart. Journ.

Micro. Sci.,' vol. xviii. P. H. Carpenter.

41. "Entwickelungs - Geschichte der Comatula Mediterranea." 'Arch. f. Mikr. Anat.,'vol. xiii. 1876. A. Gotte.

Cystoidea.

42. "On the Cystidea of the Lower Silurian Rocks of Canada." E. Billings. ' Figures and Descriptions of Canadian Organic Remains,' Decade iii. 1858.

43. " Notes on the Structure of the Crinoidea, Cystidea, and Blastoidea."

E. Billings. 'Palaeozoic Fossils,' vol. ii. 1874.

44. "Ueber Cystideen." Von Buch. 1845. (Translated in 'Quart.

Journ. Geol. Soc. Lond.' 1845.)

Blastoidea.

45. "Monographic der fossilen Krinoideen - Familie der Blastoideen."

Ferdinand Roemer. 1851.

(See also the works by Billings quoted above.) Holothuroidea.

46. "Forms of Animal Life." G. Rolleston. 1870. (For anatomy of Cucumaria pentactes, pp. 145-158.)

47. "Reisen im Archipel der Philippinen." C. Semper. 1868.

48. "Beitrage zur Anatomie und Systematik der Holothurien." 'Zeitschr. f. Wiss. Zool.' E. Selenka. 1867-68.