On the Scattered Skeletal Remains of Holothuroidea. 189 



oidea. Many more might be cited, but I have entered thus 

 minutely only with a view of showing with which type the 

 fossil remains about to be described approximate closest.* 



One fact may perhaps have a tendency to render the 

 researches of the palaeontologist amongst the extinct Holo- 

 thuroidea of less value than they otherwise might be — the 

 alteration which takes place in the form of the plates and 

 spicules during development. It has been shown by M. 

 Quatrefagesi" that in Synapta the plates before full develop- 

 ment do not possess their characteristically ovate outline, but 

 are wanting in an entire and defined margin, the plates being 

 thus irregularly formed. Similarly, the anchors are at first 

 represented only by the shaft, the flukes and the proximal 

 transverse piece being afterwards acquired. On this subject 

 Messrs S. P. Woodward and Lucas Barrett remark — ''First, 

 We find a simple and slender spiculum, then another, 



* The particulars tiere cited are to be found in tlie following works and papers : 



Qiiekett, J. — "Lectures on Histology," 8vo, vol. ii., 1854, pp. 236-247 ; 

 Griffith, J. W.— "The Micrographic Dictionary," 1856, p. 624, etc.; 

 Herapath, Dr W. B. — On the Genus Synapta, with some new British Species 

 (Quart. Jour. Micro. Science, 1865, v., pp. 1-7) ; Woodward, S. P., and L. 

 Barrett — On the Genus Synapta, etc. (Annals Nat. Hist., 1859, iii., pp. 214- 

 221); Gray, Dr J. E. — Description of ^^o^^a^ocZma, a new Genus of Echino- 

 dermata (Annals Nat. Hist., 1853, xi. , p. 301); Koren, J. — Beskrwelse over 

 Thyone fusus og Cuvieria squamata (Nyt Magazin for Naturwidenskaberne, 

 Christiania, 1845, iv., pp. 203-225) ; Quatrefages, A. de — Menioire sur la 

 Synapte de Duvernoy {S. Duvcrncca, Quat.), (Ann. des Sc. Nat, Zoologie, 

 1842, xvii., pp. 19-93, t. 2-5) ; Duben, M. W, von, och J. Koren— Om Holo- 

 thuriernas Hudskelett (Kongl. Svenska Akad. Handlingar, 1844, pp. 211- 

 228, t. 4, 6) ; Held, J. — Ueber die in die Haut der Synapten einige lagerten 

 Kalkorper (Viertel jahrs Naturforsch Gesellsch, Zurich, 1857, ii., pp. 243- 

 271, t. 2) ; Pourtales, L. F.— On the Holothurise of the Atlantic Coast of the 

 United States (Proc. American Assoc. Adv. Science, 1851, p. 8) ; M'Intosh, 

 Dr W. C. — Observations on the Marine Zoology of North Uist, Outer 

 Hebrides (Proc. Roy. Soc, Edinb., 1866, v., pp. 600-614) ; Semper, Dr C — 

 "Keisenein Archipel der Philippinen — Holothurien, 4to, Leipsig, 1868; 

 Frey, H. — Ueber die Bedeckungen der Wirtellosen Thiere(Gottinger Studien, 

 1847, pp. 709-810 ; Echinodermen, p. 748) ; Forbes, Professor Edward— 

 " British Starfishes," 8vo ; Lesson — "Centurie Zoologique," 8vo, Paris, 1830 ; 

 Jaeger — " De Holothuris," 4to, Turici, 1833. 



I am also indebted to my colleague Professor F. J. Bell, etc., for an oppor- 

 tunity of examining a number of recent examples of Holuthuroid plates in the 

 National Collection. 



t Ann. de Science Nat, Zoologie, 1842, xvii., t 2-5. 



