mm Rebou^id 19V/ HARVARD UNIVERSITY LIBRARY OF THE MUSEUM OF COMPARATIVE ZOOLOGY GIFT OF Pr L de Kon;HC/< I S 00 i %.9-v k^ THE RAY SOCIETY INSTITUTED MDCCCXLIV. u^-^ LONDON MDCCCXLVI. THE ORGANIZATION OF TRILOBITES, DEDUCED FROM THEIR LIVING AFFINITIES; ^pstcmatic l\e\)iclo of tijc ^ptcttö l)tt|)crto ticöcriljcti. HERMANN BURMEISTER, M.D. PH.D. OEDINARY PBOFESSOR OF ZOOLOGY, AND DIKECTOK OF THE ZOOLOGICAL MUSEUII IN THE UNITED IIUEDKICIIS UNIVEHSITY OF HALLE-WITTE>BERG ; COllRESPONUING MEMBER OF TttE ROY'AL ACADEMY OP TURIN ; MEMBER OF TUE IMPERIAL ACADEMY NATUR.E CURIOSORUM ; OP THE ROYAL RUSSIAN SOCIETY OP NATURALISTS OF MOSCOW ; OF TUE PHYSICO-MEDICAL SOCIETY OF ERLANGEN ; OF THE NATURAL HISTORY SOCIETIES OF BERLIN, HALLE, ALTENBURG, HAMBURGH, AND THE HARTZ ; OF THE ENTOMOLOGICAL SOCIETIES OF LONDON, PARIS, STETTIN, PENNSYLVANIA, ETC. ETC. EDITED FROM THE GERMAN, PROFESSOR BELL, F.R.S. PROFESSOR E. FORBES, F.R.S. LONDON : PRINTED FOR THE RAY SOCIETY. UDCCCXLTI. PRINTED BV C. AND J. ADLARD, BARTHOLOMEW CLOSE. '/ o The Treatise on the Organization and Classification of Triloljites, 1)y Professor BuRMEiSTER, HOW presented to the members of the Ray Society, is not merely a translation of the orij^final German edition published at Berlin in 1843, but a new edition, revised, augmented, and in part rewritten by the distinguished Author himself, who has most kindly endeavoured to render the Ray version as complete as possible by embodying all the information which had accumulated since the publication of the German edition. Through the aid of Professor Burmeistcr the Society has been enabled to procure impressions from the original and very beautifid plates. These have also been revised by the Author, and several important figures added. The translation has been executed, under the superintendence of the Editors, by Dr. Hermann MLx. In the revision of the first section of the work, they have been kindly assisted by Professor Ansted. The translation, especially of the systematic part, is nearly a literal one ; such being, in the opinion of the Editors, most likely to convey the sense of the Author, although elegance of expression may occasionally have thereby been sacrificed. They have carefully abstained from altering any expression of the Author's meaning, and even where they might dissent from his Aaews, have preferred silence to the intrusion of their own opinions. The notes they have added are all of an explanatory or supplementary nature, and especially such as may prove useful to the English reader. The Editors feel that they need not dwell on the great importance of the volume which has been committed to their charge. As a dissertation on a most- diflicult tribe of fossil Articidata by an eminent Zoologist, deeply versed in the organization of the great class to which it belongs, the work assumes an importance which can rarely be accorded to palffiontological essays treating of the remains of Invertebrate Animals. THOMAS BELL, EDWARD FORBES. London: December 18-16. BIBLIOGRAPHY. 1G98. Edw. L/iuytl iu the Pliilos. Transact., vol. xx, No. 24-1, August. Page 279. (First and oldest paper on Trilobites.) 1699. Litliophylacii Britannici Ichnographia, seu lapid. etc. Londini (also Lipsise), 8vo, Ed. I, pag. 90, Ed. alt., O.von. 1760, 8vo. 1700. Car. Leigh, A Natural History of Lancashire, Cheshire, and the Peak in Derbyshire. Oxt'ord, 1700, fol. 1702. /. J. Scheuchzer, Specimen Lithologife Helvetise. Turici, 8vo. 1708. C.N. Lange, Historia Lapidum Figuratorum Hclveti£e. Veuet. fol., p. 110. 1709. Tractatus de Origine Lapidum Figuratorum. Lucern. -!to. 1711. L. I). Heirmaun, Maslographia, Brigfe, 4to, p. 214, No. .50, Tab. IX, Figs. .00, 11,41, 12, 31. 1718. J. J. Scheuehzer, Oryctographia. Turici, 4to, p. 316. *1729. M. V. Bromell, Lithographia Suecana, in the Actis Liter. Suecife, Upsal, vol. ii, 4to, p. 408 scq. ; a separate edition of it. Holm, and Lips., 1740, 8vo, p. 76. *1732. Fr. E. Briichmmi, Centur. Epist. Itinerar. Wolfenh. 4to; Epist. 23, Tab. II, Figs. 1-7 (1732); and Epist. 64, Tab. Ill, Fig. 5 (1737). 174;"). Linneeus, Oeliindska och Gothläudska Resa. Stockholm and Upsal, 8vo. 1747. Wästgötha Resa. Stockh. 8vo. *1748. J.L. WoUersdorf, Systema Minerale, in Latin and German. Berhn, 4to, p. 42. *I750. Ch. Lijttelton, in the Philosoph. Transact., vol. xlvi. No. 496, Nov. and Dec, p. .")98. Ch, Mortimer, iu the same, p. 600. 17Ö3. E. Mende: Da Costa, in the same, vol. .xlviii, pt. I, p. 286, No. 42. * Linneeus, Museum Tessiniauum. Holm., fol., p. 123, Tab. XII. *17.i4. 3V. J. Torrubia, Apparato para la Historia Natural Espanola. torn, i, iMadr., fol., p. 83, § XIII, No. 96, 4to. * ■ ■ translated into German by Ch. G. v. Murr. Halle, 1773, 4to, p. 91, §"XCVI, 10.5. 4to. * 17.56. J. G. Lehmann, Versuch einer Geschichte von Flötzgebirgen. Berhn, 8vo, p. 73, Tab. I, Figs. A B. 17.57. Linnteus, Skanska Resa. Stockh. 8vo, p. 121. * Guettard, Memou'. sur les Ardoises d' Angers, in the Histoir. de I'Acad, des Scienc, Ann. 1757, nouv. cent. Tab. XV, p. 82 seq. (I made use of the reprint, Amsterdam, 1768, 8vo, p. 76-128, Tab. VII-IX.) Gen:mar, Beschreibung einer Versteinerten Muschel mit dreifachem Rücken. In den Arbeiten einer vereinigten Gesellsch. in der Ober-Lausitz von den Geschichten der Gelahrtheit. (Description of a petrified shell with a treble ridge. In the Transactions of a Society in the Upper Lausitz.) Lobau, 8vo, pt. II, p. 785, III, p. 185, Figs. 17-21. 1759. Liniuevs, PetriÄcatet Entomol. Parodoxus, etc. etc., copied in the Act. Reg. Acad. Scient. Holmiens, 8vo, p. 19, Tab. I, Figs. 1-4. 1763. Joh. With. Ballmer, Naturgeschichte des Mineralreiches. (Natural History of the Mineral Kingdom.) *1766. D.J. G. Lehmann, De Entrochis et Asteriis, m the Nov. Comm. Acad. Scient. Imper. Petropolit, torn, x, (for 1764,) p. 429 .seq. § XU, Tab. XH, Figs. 8-10. 1767. Darila, Catalogue Systematique et Raisonne des Curiosites de la Nature. Paris, 8vo, Fig. vols, i-iii. * Neues Hamburger Magazin, II Stück. S. 410. (New Hamburgh Magazine, pt. II, p. 410.) *1768. C.F. rr(i/c/i-ens), Nachricht von seltenen Versteinerungen, in 3 Sendschreiben, etc. Stralsundisches Magazin, vol. i, p. 267, 8to. (Information on Rare Petrifactions, in three letters. Stralsund Magazine, vol. i, p. 267. 8 ; also separately reprinted under the above title, 1769, 8vo.) 1769. Zeno, Von den Seeversteineningen und Fossilen bei Prag, in dessen neuen Physikalischen Belustigungen, Prag. 1769, 8vo. (On Slariue Petrifactions and Fossils near Prague, in his new Physical Entertaniments, Prague, 1769, 8vo.) *I770. J. Th. Klein, Specimen descript. petrefact. Gedanens. Nuremberg, fol.. Tab. XV, Figs. 3-7. *1771. Joh. Imm. Tf'alch, Naturgeschichte der Versteinerungen, zur Erläuterung der Knorr'schen Sammlung. Niirnb. fol. Theil II, S. 95 (1768), and Thcü III, S. 120 (1771). (Natural Historv of Petrifactions, to illustrate Knorrs Collection. Nuremb. fol. pt. II, p. 95 — 1768, and pt. Ill, p. 120-1771). (The part published by Knorr, 1755, contains no Trilobites.) * The works indicated by * I have consulted myself. — .\eTHOR. viii BIBLIOGRAPHY. *17"3. Joh. Beckmann, De Reductione Rerum Fossilium ad Genera Naturalia Prototyporum. In tlie Nov. Comment. Soc. Reg. Scient. Götting. vol. iii, p. 2, p. 100 seq. *1775. Gr. V. K{inshj), Schreiben an J. Edl. v. Born, in den Abhandl. einer PrivatgeseUsch. in Böhmen. I Bd. S. 243, seq. mit. Abbildungen, 8vo. (Letter to J. Edl. v. Born, in the Transactions of a Private Society in Bohemia, vol. i, p. 243 seq. with illustrations.) *1781. 3/. T. Briinnich, Beskrivelse over Trilobiten. In den Nya Sanding af det Kong. Danske Widensk. Skrifter. Kiobeuh. 4to, i, p. 384. *178j. A. Modeer, Anmerk. über Märkische Versteinerungen. In den Schrift, der Berl. Gesellschaft natnrf. Freunde, 6r Bd. S. 247, Tab. II, Figs. 1-12. 8. (Remarks on Fossils from the Mark. In the Transactions of the Berlin Society of Naturalists, vol. vi, p. 247, Tab. II, Figs. 1-12. 8.) *1793. J. C. Gehler, De quibusdam rarioribus Agri Lipsiensis Petrificatis, spec. I. Lips. 4to. 1807. Jul. de Tristan, in the Journal des Mines, vol. xxiii. No. 133, p. 21. *1810. Fr. Blumenhach, Abbildungen Naturhistorischcr Gegenstände. (Figures of objects of Natural History, I Cent. Tab. L. Gottingen, 8vo.) * F. Fr. V. Schlotheim, über Tril. Cornigerus, in Leonliard' s Taschenbuch für die gcsammte Jlineralogie, vol. iv, p. 1. Frankfort, 8vo. *181 1 . Jam. Parkihson, Organic Remains of a Former World, vol. iii, p. 263, pi. XVII, Figs. 1 1-19. London, 4to. *1820. E. Fr. t\ Sehlotheim, Die Petrefaktenkunde auf ihrem jetzigen Standpunkte, etc. (Paleontology in its Present State, etc. Gotha, Svo, p. 39.) *I821. P. A. Latreille, Affinites des Trilobites. Mem. du Mus. d'Hist. Natur., torn, vii, p. 22, 4to, and Annal. des Seienc. Phys. deBruxelles, torn, vi, 350, seq. * r. Aiidoiiin, Recherches sur les Rapports Natureis qui existent entre les Trilobites et les Animaux Articules. Annal. des Seienc. Physiq. de Bruxelles, tom. viii, p. 233, 1821 ; Isis, 1822, I, 87-104, Table I. * TTahlenliert/, Petrificata TeUuris SuecanEe. Nova Acta Reg. Soc. Scient. Upsal, tom. viii, 4to, p. 18 seq. Tab. 1 and II. *1822. A. Broyniart, Histoire Naturelle des Crustaees Fossiles. Paris, 4to. Ch. Stokes, in the Transactions of the Geol. Soc. of London. First Series, vol. viii, p. 208, pi. XXVII. *1823. E. F. V. Sehlotheim, Nachträge zur Petrefaetenkunde, part II, p. 1. Gotha, 8vo. 1824. J. W. Dahnann, in the Kongl. Swenska Academ. nya Handling, (for 1824,) p. 370. Entomostr. Actinurus, Tab. IV, Figs. 1-4. (Has also been published in a separate form.) * Bckay, in the Annals of the Lyceum of Nat. History of New York, vol. i, p. 174. (An extract from it appeared in the Isis, 1832, p. 1072); and also in the Isis, vol. i, p. 375, 1825; on Eurypterus, (Isis, 1832, p. 564, Tab. IX.) * F. W. Honinffhaus, on Calym. Macrophthalma. Isis, vol. i, pp. 464, 534, and 986. 1825. Koniff, Icones Sectiles, etc. London, 4to. H. Bronn, in Leorihard's Taschenbuch, No. 4, p. 317, Tab. II. (The author here distinguishes Cal. latifrons and Cal. Schlotheimii.) — - — Graf. V. Sternberg, Verhandlungen d. Gesellschaft d. vaterländischen Museums zu Prag. (Transactions of the Society of the National Museum at Prague, 3 vols. Tab. I, Fig. 3. Uebersicbt der in Böhmen bisher aufgefundenen Trilobiten. (Synopsis of the Trilobites hitherto discovered in Bohemia.) * E. Eichwald, Observationes Geognostico-Zoologicae per Ingriam Marisque Baltici Provincias, nee non de Trdobitis. Casani, 1825, 4to. (Noticed in Leonhard's Taschenbuch, 1828, 104.) *1826. Bar. v. Sehlotheim, in the Isis, page 315, Table I, Fig, 8-9. On Tril. Esmarkii and Tr. granura. * G. Be Razoumoivskij, Quelques Observations sur les Trilobites, in the Annales des Seienc. Natur, par. V. Audouiu and A. Brogniart, vol. viii, p. 186 seq. pi. XXVIII and XXIX. * E. W. Dalmann, on Palseaderna eller de sa kallade Trilobiterna. Stockh. 1826, 4. Translated into German by Fr. Engelhart. Nuremb. 1828, 4to, (with the original plates.) 1827. Pay/on, On the Trilobites of Dudley. London, 4to. • Ch. Boek, Notitser til laeren ora Trilobitern, in the Mag. for Nat. Science , fiirst Series, vol. i, part I. Noticed by Count Sternberg in the Trans, of the Soc. of the National Museum, at Prague, 1833, p. 45. Stecheyloff, Journal für neue Entdeckungen im der Physiologie, Chemie, Naturgesch. und Technologie. (Journal for New Discoveries in Physiology, Chemisti-y, Natural History, and Technology). St. Petersburg. Nos. I and 2, (in the Russian language.) 1828. Ueber Boek's Untersuchungen, Auszug von Bronn, in Leonhard's Zeitschrift. Jahrg. 1828. (On Boek's Researches, extract by Bronn in Leonh. Journal ; Annual Series for 1828, p. 114. Note.) * A. Gold/nss, Oljservations sur la place qu'occupent les Trilobites dans le Regne Animal. Annales des Seienc. Natur, etc. tom. xv, p. 83, 8vo, pi. II. *1829. Fr. Jukes, on a new Trilobite from Great Barr in StaiFordshire (Bumasfes harrienses, March.) in Loudon's Mag. of Nat. Hist. vol. ii, p. 41, and in Silliman's Ametic. Journ. of Science and Arts, 1832, vol. xxiii. No. 1, p. 203. Also in Leonhard's Zeitschuh, 1833, 6. 1830. E. Eichivuld, über die fossilen Podozoen und Cephalopoden, in den Russisch-Polnischen Provinzen (on the fossil Podozoa and Cephalopoda in the Russian-Polish provinces) ; from his Zool. Special. Russiee, &c. Wilnoe, 8vo, vol. i, p. 1, 323. (Nothing new ; some improved synonyms noticed in Leonh. Journal, 1832, 122. Vol. ii contains the Vertebrata, 1831 ; likewise noticed in the above Journal, 1833, 708). *1830. C. II. Pander, Beiträge zur Geognosie des russischen Reichs. (Contributions to the Geology of the Rus- sian Empire.) St. Petersburg, 4to, Fig. c. (Leipzig, L. Voss, 1839.) BIBLIOGRAPHY. ix *]KW ITmiiujIiaus, in the Isis, p. 1)5, Table I, Fig. 2. a— c. on Cixl. macrophthahna. Also in Leonh. Jahrb. 1831, p. ;«i. * Gr. K. V. Sternheri), über die Gliederung und fiisse der Trilobitcn. (On the articulations and feet of Trilobites.) Isis, 1830, JUi, Table V, Fig. 1-3. 1S31. Scolder, respecting Ediotea, in the Edinb. Journ. of Nat. Science, vol. iii. Hiiiicßlits Chemische Analyse der Deckeltheile der Entomostraciten oder Trilobiten. (Chemical Analysis of the erustaceous parts of the Eutomostracites or Trilobites. In Schweiger s Journ. of Nat. Science, and Isis, 1831, p. 341). J. D. Smverhy, i)u English Trilobites. In Loudon's Mag. of Nat. Hist., vol. iv, p. 53 seq. Also in Leonh. Journal, 1833, G2-1. * II. V. Meyer, on Calymene requalis, in Nova Act. Phys. Med. a. C. L. C. n. c. XV, 2, 100. M832. Jac. Green, a Monograph of the TrUobites of North America. Phil. Svo, (published by James Brano, see also Leonh. Journ. 1836, p. 451). *1833. J. G. Zenker, Ueitriige zur Naturgeschichte der Urwelt. (Contributions to the Nat. Hist, of the Ancient World. Jena (Mauke), 4 to, c. Fig. * Gr. i\ Sternberg, in the Verhandlungen der Gesellschaft des vaterländischen Museums zu Prag. S. 45. Ueber buhmische Trilobiten. Angezeigt in Leoiih. Zeitschr. 1835, S. 727 seq. (Transactions of the National Museum at Prague, p. 45. On Bohemian Trilobites. Also in Leonh. Journal, 1835, p. 727 seq.) * Esmark, in the Mag. f. Natmvidenskab. Anden Raekkes, i, 2, 268, Table VII. *1834. J. V. Thompson, Zoological Researches, No. V. Cork, 8vo, c. Fig. * K. V. Kloden, die Versteinerungen der Mark Brandenburg. (Petrifactions of the Duchy of Brandenl)urg. Berlin (Liideriz) 8vo, p. 104 seq. Fr. Jukes, in London and Edinb. Philosoph. Mag. iv, 376. On a new Trilobite from Coalbrook-dale. * J. Green. Descriptions of some new North American Trilobites, in Sillimans Amer. Jour, of Sc. and Arts, 1834, Jan. XXV, 2, 324-337. Also in Leonh. Zeitschr. 1836, 461 seq. (Cal. odontocephala. As. astragalotcs. As. tetragonocephalus. Par. Ilarlani). J. Green, Description of a new species of Trilobite, As. crypturus, (without a head !), in the Transactions of the Geolog. Society of Pennsylvania, 1834, I, 37-39. *1835. H. G. Bronn, Lethaea geognostica, etc. Stuttg. 8vo, 2 vol. Fig. * M. Sars, in the Isis, 333 seq. über einige neue oder unvollständig bekannte Trilobiten. (On some new or imperfectly-known Trilobites, with plates. Table IX-X.) Published in Leonh. Jahrb. 1836, 463. * HOninghaus, on Calymene arachnoides, Crefeld, 4to, Fig. * Harlan, Medical aiid Physical Researches. Philad. 8vo, Fig. p. 400 (new Trilobite) and p. 297, (Euryp- terus) seq. (Synops. of Tril. of North America.) *1836. W. Buck-land, Bridgcwater Treatise. London, vol. ii, Svo, Fig. Translated into German by L. .igassiz. *1837. /?./. il/i"'cÄ/«o«, the Silurian System. London, 4to, vol. ii. Plates. * ■ Quenstedt, in Wicgmann's Archiv, vol. i, p. 337. Zahlenverhältnisse der Trilobiten. (Numerical propor- tions of the TrUobites). Pubhshed in Leonh. Journal, 1838, p. 485. * W. Ilisinger, LethiEa suecica, etc. Ilolmise, 1837, 4to, c. suppl. i and ii, (1840). (Extract from Dalmanns work, together with an appendix of new species and plates.) /. Green, on Cryphaeus in Sillim. American Journal of Science and Arts, 1837, xxxii, 345-49. See also, Leonhard's N. Jahrb. 1838, 363. On two new Trilobites. Cal. phlyctainodes and Trinucleus platypleurus. In the same Journal, p. 167-169 ; see also p. 363. Milne Edwards, sur les Affinites des Trilobites. L'Institut. p. 254. 1838. Chr. Boeek, Uebersicht der bisher in Norwegen gefundenen Trilobiten. (Synopsis of the Tiilobites hitherto discovered in Norway.) Keilhau, Gaea Norwegica, i, p. 138-145. Only known to me from the notice in Leonhard's N. Jahrb. 1841, 724. *1839. //. F. Emmerich, de Trilobitis, dissert, petrefact. inaug. etc. Berolini, 7, Fig. * J. Green, Remarks on the Trilobites, in Sillim. Am. Journ. of Sc. and Ai'ts, vol. xxxviii, No. I, p. 35, Fig. c. Extract from Buckland's Geology and Mineralogy. *1839. J. Green, on a new Trilobite : Asaphus diurus. In Sillim. Amer. Jour, of Sc. and Arts, vol. xxxviii, p. 40. * G. Fischer De Waldheim, Notice sur I'Eurypterus de Podohe, etc. Moscow, 4to, Fig. Noticed in Leonh. N. Jahrb. 1840, 736. *1840. L. r. Buch, Beiträge zur Bestimmung der Gebirgsformationen in Russland, in Karsten s Archiv für Mine- ralogie, etc. Bd. XV. Beriin, 8vo, 127. (Contributions to the History of the Geology of Russia, in Karsten s Archiv for Mineralogy, etc. vol. xv, Berlin, 8vo. Noticed iu Leonh. N. Jahrb. 1840, 127. * Milne Edwards, Histoire Naturelle des Crustaees. Paris, 8vo, vol. iii, p. 285 seq. * G. Gr. zu Münster, Beiträge zur Petrefactenkunde. (Contributions to Paleontology.) Bayreuth, 4to, vol. iii, p. 34 seq. Noticed in Leonh. N. Jahrb. 1840, 135. *1842. Vol, V, p. 112 seq. *1840. //. G. Bronn, über die mit Homalonotus verwandten Trilobiten-Genera. (On the genera of Trilobites related to Homalonotus.) Noticed in Leonh. Journal, 1840, 445. *1841. A. Goldfuss, Beiträge zur Petrefactenkunde. (Contributions to Paleontology, in /, A Synopsis of the Characters of the Carboniferous Fossils of Ireland. Dublin, 4to, 1844. R. I. Mxrehison, E. de Verneuil, and A. de Keyserling, Geology of Russia, vol. ii, Paleontology, p. 376, plate XXVII. (One new species, Phillijasia Ouralica, is described.) 1845. R. Griffith and F. MCoy, A Synopsis of the Silurian Fossils of Ireland, 4to, 1846. Dublin, 1846. J. Barrande, Notice preliminaire sur le Systeme Silurien et les Trilobites de Bohemie, 8vo, 1846. T. Oldham, on Griffithides glohiceps, in Proceedings of the Dublin Geological Society for 1846, and Plate.] CONTENTS. PAGE Preface ........ ] Introduction ....... 3 CHAPTER I. On the Visible Structure of the Body of the Trilobites . . 13 CHAPTER II. Affinity of the Trilobites to the Existing Articulata . . .31 CHAPTER III. Systematic Arrangement of the Species .... 53 Appendix . . . . . . . .112 Supplementary Appendix by the Editors .... 121 Description of the Plates . . . . . .129 Index of Genera and Species enumerated by the Author . . 133 PREFACE. Having given a sketch of the plan of my present work in the subsequent introduction, it will be superfluous to enlarge further upon it here. My treatment of this subject in a merely zoological point of view is partly owing to the very natural consideration that these most ancient remains of the animal world not only admit of such a mode of contemplation, but, indeed, demand it, if the subject is to be thoroughly worked out ; but partly also no doubt it is to be attributed to the entirely zoological direction of my studies. Works on fossils are undoubtedly the more profound, the more the autlior has penetrated into the study both of Geology and Zoology ; but who, excepting Cuvier, can boast of such a universality ? I therefore preferred to relinquish the geological investigation of the subject entirely, and not enlarge on the various strata containing Trilobites, and I would also request the reader not to lay any great weight on the geological observations he will occasionally meet with in the course of the work ; for they may sometimes have been based on the views of others imperfectly understood, and for this and other reasons they must be considered as not to be implicitly relied on. On the other hand, I would venture to hope, that my zoological system of arranging the various groups may meet with the appro- bation of my readers, and that I may have succeeded in my endeavours to lay the foun- dation of a single and correct view of the subject, which may supersede the many fluctu- ating ones hitherto prevailing. My object indeed included both these departments of the subject, but I cannot answer for the correct designation of many specimens supposed to be of identical species, but frequently no doubt imperfectly determined, or of others presumed to be new, the originals of which I was not permitted to examine. I have indeed received much assistance from German authors, but have often not been so fortunate with regard to those whose species appeared to me the most questionable, and in such cases the determination was frequently left to the view I took of them on my own personal inspection. I have seen everything connected with my object contained in the collections of Berlin and Halle, and I have also received valuable contributions from Mr. Bocksch in Silesia, from Captain von Charpentier, and from Mr. Honinghaus at Crefeld. On the other 1 2 PREFACE. hand, I have had but few opportunities of examining original specimens from England and America. My present work therefore certainly ought not to be considered as complete ; it will unquestionably admit of much improvement, and for this purpose I should gratefully receive any assistance, especially of original specimens of species hitherto unknown to me, even if it were only for temporary inspection. Indeed I should be satisfied with good figures of such specimens, provided they were accompanied by explanatory descriptions. Such illustrations being rare, I have made it my principal object to render the plates contained in this work as perfect as possible. I have had the good fortune to meet with an artist in the person of Mr. A. Andorif, of Berlin, whose talents and whose execution of the engravings are such, that I can, without the slightest hesitation, recommend the plates, which were executed by him, as patterns for imitation to all artists. Every person acquainted with the subject will undoubtedly agree with me, that better and more beautiful representa- tions of Trilobites, or figures more true to nature in every respect, are not in existence. Halle; May ^th, 1843. INTRODUCTION. SECTION I. Researches on organic bodies of former ages are equally interesting and necessary to the Zoologist and Geologist, although their respective objects in pursuing such studies are different. For whilst the Geologist is generally satisfied with establishing the difference or identity of the species found in the several strata, the Zoologist insists rather on a perfect knowledge of the animal in question, to enable him thereby to determine the modi- fications which the entire animal organization has experienced in the successive periods of the earth's formation. These entirely different interests of the observers explain in some measure why the knowledge of extinct animals necessarily remained in a defective and imperfect state so long as no competent Zoologist occupied himself with the subject, and indeed, even a Zoologist who is so qualified can only give satisfactory information if perfectly acquainted ^ath the organization of the living allies of such animals, and that in most minute detail. This indeed is sufficiently proved by Cuvier's great researches in the department of Palfeozoology, and the example of this great man has led modern Geologists who study fossils to the conviction of the neces- sity of profound zoological studies, and has convinced them that an investigation, at least of the higher animals, cannot be instituted without accurate zoological knowledge. The truth of this principle has, however, been less acknowledged with regard to the lower animals, and least of all with respect to the Articulata, because their number and importance in relation to geology is, upon the whole, comparatively slight, whilst their organization also has been particularly studied only by a few Zoologists, and by them only recently. There is no family, however, among the Articulata of a former world which in every respect deserves so much attention as the family of the Tnhhites ; and consequently this tiibe has been the subject of much research, but our acquaintance with their organization is still very defective, either because all the more recent observers, from a consciousness of their imperfect knowledge, did not enter into the study of them in a zoological point of view ; or because, from the deficiency of their zoological studies, they could not, on attempting to do so, disguise their ignorance on those points. And yet it is undeniable that wc may obtain as clear and perfect an acquaintance with the organization of these creatures as of the Mammalia, since the organization of a crustacean being evidently less complex than that of a mammal, a perfect idea may be developed with even greater completeness from the existing fragments of the Trilobites, than was possible in Cuvier's representation of the Vertebrata. INTRODUCTION. SECTION II. The object of the present work is the carrying out such an illustration of the subject in all its parts. Having almost e.xclusively occupied myself with the study of the Articulata, especially of insects and crustaceous animals, I have collected the materials upon which I based my undertaking with diligence and circumspection ; I have most carefully tested all analogies as well as more remote relations ; I have frequently consulted with my friends ; and I have thus gradually pi'ogressed with my subject until the present moment, when leisure is at last afforded to me to devote myself entirely to the work, and to present it to the public in its present state. Previous, however, to communicating my own researches, I beg to lay before my readers a short sketch of the information which has hitherto been known respecting the Trilobites. SECTION III. The first author who wrote on these remarkable animals was Edward Lhwyd, Curator of the Ashmolean Museum at Oxford. He discovered two fragments and one entirely preserved specimen of the Ogyyia Buclm, near Llandeilo, in Carmarthenshire, of which he sent drawings to the well-known zoologist Martin Lister, also a superintendent of the Ashmolean Museum. The latter gave them to the public in the twentieth volume of the ' Philosophical Transactions.' Lhwyd owns in his letter that he did not know what to make of tliese fragments ; in Fig. 8 of the accompanying plate we recognize, however, with tolerable certainty, a cephalic shield of the genus Trinudeus of Murchison, {CryjjtoHflnis, Green,) and the Ofjijgia (Fig. 15) is perfectly evident ; but Lhwyd explains it to be the skeleton of an unknown fish. The same author published in the year following his ' Ichnographia Lithophyl. Britann.,' and therein enumerates thirty specimens already observed by him ; but those before alluded to are again mentioned, the first under the name of Trinudeus fimbriatus vuhjaris, the subsequent Dudley fossil as Bur/Iossa curta sirif/osa. These communications, the earliest we possess on the Trilobites, were soon followed by others in all parts of Europe, but although the number of observations was thus increased, the knowledge of these animals made no progress, principally because correct comparisons with living forms were wanting. They therefore appear in subsequent authors merely under newly-invented names, which partially indicate very incorrect comparisons, the inappropriateness of which is, however, excusable, since the observers of the Continent were only acquainted with mutilated specimens, or with mere caudal shields, and therefore were much inclined to mistake these remains for shells. One author (Hermann) calls them Fcctunculites trilohis imbricatus, another (Scheuchzer) compares them with Patella, a third (Bromell) fancied that he recognized in them the remains of insects, while a fourth (Brückmann) also compares them with shells, call- ing them Armata veneris, and so also does Waltersdorf, who, in his System of Minerals, styles them ConcJiitcs irihlus, connecting together the different designations of his predecessors in " Käfermuscheln," and " Muschelsteine." But the correct view of the natural affinity of the Trilobites was announced at almost the same period. Their anomalous form induced a INTRODUCTIOX. 5 number of collectors to search for them in England, where the most beautiful and perfect specimens have always been found, and their admirable condition in that country readily caused the impression that they must be Articulata to gain ground. We learn from Dr. Shaw, Lister's successor in O.xford, that he took them for a caterpillar (eruca), and Ch. Lyttleton, who laid new specimens before the Royal Society of London, coincides in this view ; Ch. Mortimer, on the other hand, on an occasion of some new specimens of the Dudley fossil (as the Trilobites were usually called in England, from the principal locality where they were found) having been sent by Dr. Pocock, expressed the opinion that they appeared to correspond most with the Monoctdus apus, Linn., shortly before described by J. Th. Klein, in the ' Transactions of the Royal Society' (vol. xl, p. 150). As Klein had given the name of Scolopendra aqualka scutata to this animal, Mortimer proposed the designation of ScoJopendrm aquaticcB scutata oßne animal petrifcatiat/, which, however, even on account of its length, could not meet with any great approbation. The next English author on the Trilobites, Emanuel Mendez Da Costa, endeavoured therefore to find a better name, and on again laying a beautifully preserved specimen before the Royal Society, he declared it not only to be a crustaceous animal, but also to be one nearly related to the sea-louse, and he called it Pediculus mariniis major trilobus. This name of sea-louse was then employed to designate several of the larger Isojwdes, which live on fishes as parasites, and from amongst which Linnaeus constituted his genus Oniscus. Linnaeus, whose system and reform of the science just then began to be appreciated, had consulted with Mendez Da Costa respecting the Trilobites in the same year, and designated all the species belonging to it as modifications of his Entoniolithm paradoxus, deciding himself in favour of their near affinity to Monoculim npus. This view of the great naturalist, which is expressed in all the editions of the ' Systema Naturae,' certainly ought to have led those who knew little more of the subject than the fragments lying before them to a correct conception of the afiinity ; but their very ignorance of the points of comparison made them overlook it. Several authorities now again declared in favour of the afiinity to the Mvllasca ; but the French observer Guettard correctly enumerated the Trilobites of Angers among the Crustacea, designating them as allied to the genus Oniscus of Linnaeus. This author was, however, perfectly unacquainted with Linnaeus, and equally so with the German writers, who also have never taken any notice of him. The next writer on the subject, Father Joseph Torrnbia, having been a native of Spain, where the sciences were in a dormant state, I shall not lay any great stress upon his opinion, but he at first correctly described the Trilobites as crustaceous animals, although subsequently, misled by the inspection of Rumphius's figure of the Liiiice marina {Chiton aculcatus, Linn.), imagined the latter to be a mollusc. The treatises of the Provost Genzmer of Stargard, of Professor D. J. G. Lehmann of Petersburg, of the well-known secretary of the town-council of Danzig, J. Th. Klein, and of Professor Zeno of Prague, I may enumerate as proofs that such an erroneous conception of the nature of Trilobites has prevailed. The first termed them Conchitce ruyosi irilübi, and Lehmann,* as also Klein, adopted this designation, whilst their contemporaries enumerate them by the names of " Kiifer-muschel,"' and " Kakadumuschel." This determined anotlier, but more enlightened * In the summary of this volume, p. 56, the author ex])rcsses the same opinion as Liunseus, without, however, guaranteeing its correctness. (5 INTRODUCTION. collector to endeavour to diffuse Linnaeus's views respecting the true affinity of the Trilobites among his readers, and to prove " that the Conchologists have no longer any reason to consider the fossil which had hitherto been known by the name of a Coiichifce triloU rnyosi as a part of their science." The author of the treatise referred to, Ch. Fr. Wilkens, announced his name in the following year, and published his opinions under the title of ' Information respecting Rare Animal Petrifactions.' He treats of the numerous Trilobites in his collection with much cleverness, although with an unnecessary prolixity, and arrives finally at the well-founded result, that the name of EntomoUthus branchiopodis cancnformis marinus ought to be given to them. But the appearance of this treatise in an unknown periodical, was not calculated to attract attention, or procure credit and appreciation for it, and it is questionable whether it would ever have come to the knowledge of subsequent authors, if J. Imm. Walch had not particularly referred to it in his ' Natural History of Fossils.' It decided Walch's opinion, however, and as this diligent writer brought togetlier everything that had hitlierto been written on the Trilobites, his elaborate work became an authority on which succeeding authors might rely with certainty in the labyrinth of conflicting opinions. Being convinced of the unfitness of tlie names hitherto used, either owing to their incorrectness or their length, he proposed a new designation for them, and was the first who called these animals Trilobites, a designation, which, with the exception of Dalman, has been retained by all the subsequent authors, and therefore, being the oldest and by no means an unsuitable name, will also be retained by us. Walch, however, was not sufficiently a practical zoologist to be able to support Wilkens's \icws by additional reasons, and indeed he generally speaks more of the ideas of others than of his own opinions on the subject, and seems inclined to consider the 0/iisci as the animals most nearly allied to the Trilobites. Henceforth the opinion of the affinity of the Trilobites with the Mollusca was nearly buried in oblivion, and would probably never have been known, if its memory had not been revived again nearly fifty years afterwards by a zoologist, from whom, possessing as he did an accurate knowledge of the Articulata, one could least of all have expected it, namely, by Latreille. The next writer after Walch, John Beckmann, calls them Onisci, without any circumlocution, and Count v. Kinsky, in a letter to the Baron von Born, uses the name given by Linnaeus, while M. Th. Brunich, on the other hand, uses Trilobus, Walch's designation in an abbreviated form, and J. K. Gehler retains it in its original form. Finally, the opinion of A. Modeer, who thought that he could recognize the structure of a tube beetle, (Coccinella) in the Trilobites, at least in the heads of liattus and Olcmts, which he described, was new but erroneous. SECTION IV. Such was the state of our knowledge of the Trilobites, when the great political events which took place at the conclusion of the last and the commencement of the present century rendered all serious efforts for the advance of science impossible. During the period extending from 1793 to 1820, we only meet with three short observations on the Trilobites, of which the first is contained in Blumenbach's 'Illustrations of Natural History;' the second in Parkinson's ' Organic Remains of a Former World ; ' the third in Leonhard's ' Taschen-buch fur Mineralogie ;' in which the Baron v. Schlotheim describes a new series INTRODUCTION. 7 of Trilobites as T. coniir/crun, directing attention, according to Bcckmann's and Briinicli's example, to the necessity of distinguishing several species of these animals. This very correct view he furtlier carried out in his ' Pctrefaktenkunde' of 1820, in which he speaks of five different species, two of which, however, belong to doubtful forms. All the three authors are of opinion that the Trilobites are Crustacea, without, however, determining their more intimate affinity with any particular group. SECTION V. The year 1821 is a crisis in the literary history of the Trilobites, for a new epoch then commences, which may be designated as the period of the more accurate study of them. Four distinguished observers, Latreille, Audouin, Wahlenberg, and Brongniart, published the result of their studies in or immediately after this period, the two former only paying regard to the organization of these animals, the two latter describing the differences of the species. P. A. Latreille, the best authority on the subject of the Articulata, both with respect to the general subject and its details, might certainly claim attention to his opinion on the affinity of the Trilobites ; but he performed his task in a manner which could by no means satisfy those acquainted with the subject. After having formerly determined in favour of the affinity of the Trilobites to the Articulata (Cuv. Regne Anim., prem. ed. torn, iii), he here contradicts this opinion altogether, and endeavours to prove, by the absence of feet, that the Trilobites must be most nearly related to Chiton. He not only, therefore, overlooked the articulation of the body, pervading all parts of it, but also the eyes ; he asserts also, that if feet had been existing they must be recognizable, and from their absence draws the conclusion that the Trilobites are Mollusca. V. Audouin, who probably had only shortly before completed his work on the skeleton of the Articulata (Annal. des Scienc. Natur., pr. ed. tom. i, 1824), had also been led by these studies to the subject of the Trilobites, and soon recognized their articulate nature from the remains of the crust. But he evidently went too far in transferring the results he had so readily arrived at with regard to insects to the other groups of the Articulata, and in this he sought analogies which do not exist in reality. Indeed, even his own investigations with regard to the abdomen of the Macrura, with which, as with the thorax of the IsopoJa, he very justly compares the crust of the Trilobites, ought to have convinced him that the cpisterna and ejjimera, two portions of the thorax of insects which are separated by particular sutures, do not at all exist in the gi'oups enumerated, and that even the boundary between back and sternum is an artificial one. He nevertheless views the lateral lobes of the shell, which in many of the Trilobites are separated by an oblique diagonal furrow into an anterior and posterior half, as analogues of those parts, terming the anterior cpisternum, the posterior epimerum, and the middle part of each tergum; appellations manifestly unsuitable, since several Trilobites (e. g. Illanus) do not possess this separating furrow at all, and in no single species of them do the regions distinguished by him constitute isolated pieces connected by sutures. AVe arrive, however, in spite of these subtleties, for which there is no natural foundation, at the four following facts, namely, — 1st. That Trilobites differ only from the other Articulata in points of secondary importance, and that, beyond a doubt, they belong to this group of the animal kingdom. 8 INTRODUCTION. 2clly. Tliat they exhibit the greatest analogies with the Isopodes, particularly with Cj/mofJioa and Lit/ia. 3dly. That the want of feet seems to be a necessary characteristic of their skeleton formation, although this point still remains problematical. 4thly. That these feet, if they existed at all, were most probably connected with the branchial apparatus. An important result was evidently gained by the enunciation and establishment of these four principles, and the consideration of the last assumption especially has given that direction to future researches which is the proper result of a preliminary investigation. George Wahlenberg followed more closely the footsteps of Linnaeus than any of his predecessors, and endeavoured to maintain his view respecting the afBnity of the Trilobites, merely also changing Linnaeus's name of EntomoIifJtns into Entüwodrcic'ües. But as he was no special zoologist, and as the groups of the Crustacea in general could not be very strictly defined at that period, or their essential characters be readily distinguished from others, he did not succeed in establishing such evidence as should be incontrovertible. He believed that the Trilobites were most nearly allied to Limulus, and was inclined to transfer this similarity also to the structure of the feet. The feet of the Trilobites, in his opinion, however, were smaller than those of Limulus, and for this reason were absent in the fossils. In some shields and rings he believes that he recognizes mere membranes that had been cast oflF, there being no doubt that these animals must have cast their membranes in the manner of the Articulata. In other respects he still leaves all the species in one genus, and describes fourteen of them. The most perfect work of all is Al. Brongniart's 'Histoire Naturelle des Crustaces Fossiles,' which appeared about a year after the publication of Wahlenberg's p.aper. It was this work which first pointed to the generic differences of the Trilobites, exhibiting five genera mostly well-distinguished ; the species were more accurately determined, and the number then known was stated to be seventeen ; finally, there were here explained many facts with regard to the geological history of Trilobites more elaborately than had been done by Wahlenberg. Brongniart expresses the correct view with reference to the zoological relations, namely, that the Trilobites are most nearly related to the Bmnchiopodes among the Crustacea, and that the want of visible feet, as well as of visible antennae, accords very well with this. He does not, however, dispute the analogy with the Impodes so distinctly as the subject requires. The importance and influence of this excellent work on our knowledge of the Trilobites was exhibited immediately after its appearance, since M. Schlotheim felt himself obliged to publish an addition on this subject as a supplement to the former scanty results of his 'Treatise on Fossils ;' and in this supplement, in which he gave an extract from Brongniart's work, together with a description of some new species, the number of all the known species, including three which are unsatisfactorily described, amounts, according to his enumeration, to twenty-nine, from which, however, we must omit three, as decidedly not belonging to the family. ' INTRODUCTION. SECTION VI. Having thus traced the history of tlie Trilobites in detail, and almost completely, I shall now terminate this part of my work, since, after the publication of M. Brongniart's work, the multitude of authors increased with every year, insomuch that a mere enumera- tion of them would be not only wearisome but superfluous, since the contribution of each individual being merged in the general progress of the study, the latter only requires to be made prominent. We find, however, that the exertions of naturalists henceforward were especially directed to the establishment of species, and to the publication of new forms, and that a variety of errors have been committed in this respect, which principally originated in the defective knowledge of the structure of the body of the Trilobites, and in the imperfect fragments upon which such new species have been founded. An immense number of new names and characters has therefore certainly accumulated, but by no means in the same ratio is the number of really new facts. Even monographists of some districts in which remains of Trilobites are found, have not been able to guard against confound- ing species already known with supposed new ones. If I were now to enter upon the particular proofs of such errors, it would lead me into an investigation of the differences of species, and thereby cause subsequent repetitions ; I limit myself therefore to a short notice of those works which have excited attention, and on that account deserve a par- ticular notice. Dalman's ' Treatise,' published in I82G, is, next to Brongniart's ' Monography,' the most important work on Trilobites, but it does not add any important new facts in a general point of view, and by no means determines the zoological affinity of the Trilobites de- cisively. In the particular point of the establishment of species, it is only richer and more complete than Brongniart's work with reference to Sweden. The author's proposal to use the appellation of Palaadcs, instead of the family name of Trilobites, has met with no appro- bation, nor does it merit such, since nothing more is expressed by it than by the older name, which at least indicates correctly a portion of the family characteristics. The Trilobites, however, were made the subject of researches at many different places, almost simultaneously with Dalman, and many new forms and views were thereby more intimately explained. Dekay (1824) was the first who described the North American Trilobites in several treatises, but his results were not appreciated by the scientific men of Europe till afterwards. Count Sternberg (in 1825) described the Trilobites of Bohemia with his usual accuracy, and had in Boeck (1827) a successor equally careful and ingenious. It is to the latter that we are particularly indebted for a correct view of the facial line or suture, which extends through the cephalic shield. Payton wrote on the Trilobites at about the same period in England, but I am not able to say with what success, since I have never seen his work. Four authors were within a short time successively employed on this subject in Russia, who furnished by their joint efforts many valuable contributions. Eichwald, the earliest of them (1825), gave a perfect monography of the Trilobites of Esthonia, and also enlarged on their zoological affinities. His endeavour, however, to trace the analogy of the Trilobites with the Isopodes was not more successful than his establishment of thirteen different species was accu- rate. After carefully analysing them, we can only recognize in them four really distinct species. 10 INTRODUCTION. Razoumowsky's observations (1826) are aphoristic, and are limited only to some forms from the neighbourhood of the Ladoga Lake, all of which were already known. StscheglofFs treatise (1827), on the Trilobites of Petersburg!!, written in the Russian language, I only know through Pander's work. The latter careful observer treated the same subject (1830) with great minuteness, but without important results. He certainly succeeded in partially reducing Eichwald's species, but he himself mistook his own species, and considered them as new ones, which is not the case with any one of them. The general part of his work exhibits the greatest diligence and research, but it also shows an entire want of knowledge of living Crustacea, owing to which it was impossible for the author to communicate new and certain information on tlie structure of the Trilobites. Eich- wald, Razoumowsk}', and Pander, however, also recognized the peculiar swelling at the lower side of the cephalic shield, which lies before the mouth, first observed by Stokes, and which corresponds with the dypeiis of the Crustacea and Insects. Goldfuss (1828) en- deavoured to give information on the feet of the Trilobites, which had hitherto escaped the attention of observers, but although he explained their structure correctly in a theoretical point of view, his illustrations are not calculated to convey the idea they are intended to represent. The endeavours to trace these organs in our fossil remains must always remain unsuccessful, since it is impossible that parts of such a tender nature as we must suppose them to have been, judging from the living analogues of the genus, can have left trace of their existence. Tlieir very absence in fossils most distinctly proves their former real structure. Next to Pander's work there was published (in 1832) Green's ' Monography of the American Trilobites,' a work abounding in names and words, but as poor in really available facts. Indeed, if the author had not also caused plaster casts of his best specimens to be manufactured, it would liave been impossible to recognize even one half of the really new species from his descriptions and illustrations. This period, indeed, was rich in a number of publi- cations on the subject, the appearance of which was of no great importance to the furtherance of our knowledge, and the value of which was very correctly estimated by L. v. Buch, when he considers them as of less consequence than " two important observations of Quenstedt in Wiegmann's Archives," on which I shall soon more particularly enlarge. Among these writers we may enumerate Zenker, the more recent (1833) observer of Bohemian Trilobites, the results of whose labours were already successfully portrayed in the same year by Count Sternberg. Kloden's statements also, respecting the structure and mode of living of the Trilobites on those remains which are found in the Mark Brandenburg (1834) only contain ill-founded assertions. This certainly cannot be asserted of Sai''s communi- cations (Isis, 1835), although not all the species are new which he describes as such. We regret that the same may be said of Murchison's description of the English Trilobites, given in his great and excellent work on the ' Silurian System of the British Islands' (London, 1837). The author, being merely a geologist, has preferred allowing W. S. M'Leay to speak on the zoological affinity of these animals, but the peculiar ideas of the latter are not calculated to afford a real explanation of such questions. The division of the Crustacea, in which the AnqjJiipocles (together with the Isopodes), Trilobites, and Entomostraca are enume- rated as three subdivisions of equal value with one great principal group, which is considered as founded in nature, is not calculated to create any great confidence in the systematic talent INTRODUCTION. 1 1 of their author. M'Leay, too, on this occasion, as he lias often clone clscwhei'c, confounds the ideas of analogy and affinity, the first distinction of which in England is justly considered as his greatest and generally acknowledged merit. Another English author, however. Dr. Buckland, had not long before (183G) already explained the same subject with much genius and vigour. He believes that Scrolls, Limulus, and Bramkipus are the three genera of living Crustacea, to which the Trilobites are most nearly related, and he founds his comparison on the resemblance of general form in the first, the structure of the cephalic shield in the second, and the structure of the feet and nature in the eyes in the third. How far these assumptions are well founded, we shall subsequently investigate. I will not here touch at greater length upon the several observations of contemporary writers, as of Hönighaus, Bronn, H. v. Meyer, Hünefeldt, J. V. Thompson, Sowerby, Jukes, Esmark, Green, and Harlan, but will proceed to some more recent, more elaborate, and more important works, which form the conclusion of the researclies hitherto made. Hiesinger, in his General View of the Swedish Trilobites (1837), the first of these publications, follows Dalman's example exactly, and gives but few new facts. Quenstedt's* statement in Wiegmann's ' Archiv' (1837, 1), deserves greater attention, especially on account of the import- ance which was here first attached to the numerical proportions in the difi"erent divisions of the body, particularly of the trunk. I must, however, dispute the correctness of the author's representation of the eyes, of which he assumes two types, and also his assertion that a division of the group into genera is not yet necessary. With regard to the latter point, it should be remembered that the object of the descriptive natural sciences consists by no means in the mere registering of natural bodies, but involves the unveiling of those differences, subordinate one to another, by which nature has changed the original simple type into so many various forms. Having once correctly recognized such distinct degrees of modification, and having made out the characteristics of these modifications, we then consider them as genera, or speaking generally, as groups to which we give special names, in order to remind us of the peculiarity in the modification of the fundamental type. For this and for no other reason is it that we give names to the groups, intending simply to facilitate the interchange of ideas and experiences, just as the use of coin facilitates commercial intercourse. Quenstedt's predecessors knew this quite as w-ell as his successors have appreciated it, and made it their object to establish well-founded genera. Boeck onl)^ attempted to indicate these (in Keilhaus 'Gaea Norwegica,' 1838), reserving for himself the particular description in a ' Monography of the Trilobites,' which has long been an- nounced, but which has not yet made its appearance. Emmerich in this, howevei", has anticipated him, succeeding Quenstedt as assistant at the Mineralogical Museum at Berlin, and likewise following in the footsteps of the latter naturalist, and choosing the Trilobites as the particular object of his studies. In his carefully executed work (Diss. Inaug. Berol. 1839) the general part is certainly not much enriched by new facts or views, but the special part is written with a careful investigation of the manifold synon)'ms, and built on the gene- * I believe that I was the occasion of this statement. During a visit to the !Mineralogical Museum at Berlin, at which ]M. Quenstedt ^^as tlien assistant, I explained to him my views respecting the Ti-ilobites, their structure and their affinities, and laid particular stress on tlic importance of the numerical proportions. The statement alluded to was published a few months subsequent to that conversation. 12 INTRODUCTION. rally correct basis which Quenstedt exhibits in this respect. The group of the large-eyed species, furnished with eleven articulations, which was first recognized by the latter, was named Vhacops by Emmerich, and appears as a genus, besides eight others, of which the second {Odontopleura) is also new and well-founded, but cannot be satisfactorily recognized by the very defective illustrative figure. Emmerich has also followed his predecessor in this respect, that he extends the identity of Ilomalonotus and Trimerm, first announced by Murchison (and to which Brenn subsequently — 1840 — also added Blpleuni), to Co/ywrae, considering the group merely as a subdivision of it. He unquestionably, however, goes too far in this respect, especially when he separates from it Bipleum, which of all the three forms is most nearly related to Cali/meue. Next to this work there follows a brief but sound and valuable account of the Russian Trilobites by L. v. Buch (1840), containing a correct view of all essential characters, namely, a comparative study of the relative proportions of the head, trunk, and tail, and the relation of the separate parts to the whole. " By proceeding in this manner only can we expect real natural historical classifications, such as rise above the poor purpose of serving as con- venient indices to collections and catalogues." This is perfectly true, but the contemporary works of the Count v. Münster (1840 and 1842) unfortunately do not soar beyond that purpose, for they scarcely furnish a single perfect description of the many new species exhibited, and only indicate obscurely in the illustrative plates the real forms to which they probably belong. The paradoxical forms which Goldfuss has published (1841) offer, both in perfection of representation and description, a magnificent contrast to the last work, and cannot be too strongly recommended as a pattern to those who henceforth wish to describe Trilobites from fragmentary specimens. The newest work on this subject, one recently published by Milne Edwards, in the third volume of his ' Histoire Naturelle des Crustaces,' tom iii, 1841, embraces indeed everything connected with the subject, but, on the other hand, is by no means worthy of the name which this distinguished French naturalist has procured for himself by many excellent works. The arrangement of the Trihhites between Isojmks and Phyllopodes, which the author follows, does homage to all the different views hitherto pro- posed on the subject, and therefore does not bring the matter to a decision ; but in this case the truth lies by no means, as it often does in other cases, in the middle. Among the assumed twelve genera, several, as Pleuracanthus, Peltura, and Otarion, are founded on mis- understood fragments, and the same may be said of many species which the author copies from his predecessors without any further investigation. It is to be regretted that so pro- found a zoologist, who may justly be considered by the many as a distinguished authority, has paid so little attention to this part of his otherwise very meritorious volume, and has thus furnished a work which can only be considered valuable as a mere compilation. It certainly has not advanced us one step in our knowledge of the structure of these animals. THE ORGANIZATION OF TRILOBITES. CHAPTER I. ON THE VISIBLE STRUCTURE OF THE BODY OF THE TRILOBITES. SECTION I. The body of all Trilobites consists of three distinct divisions, which have received the denominations of cajmt, thorax, and abdomen. They may be recognized as Articulata by this characteristic alone. The first two divisions include many associated parts, constituting the cephalothorax ; but these remain separated in the Trilobites, and this circumstance not only greatly facilitates the special examination of their body, but also affords convincing information respecting their afiinity to existing species. Postponing the investigation of their affinity to the next chapter, we shall now consider the remains of the Trilobites, as they are presented for our examination. SECTION II. The remains of the Trilobites are limited to the shell and its impressions, and no softer part of their body has, or indeed could be preserved. Hence it appears to me certain that all those parts which possess the hardness of the shell, or at least were clothed by any substance as hard, must exist in the impressions of the Trilobites ; and that, on the other hand, those parts which probably existed, but which are wanting in these impressions, did not possess the firmness of the shell, and are absent on that account. If, therefore, as is the case, we no longer perceive the entire abdominal sui'face of the Trilobite body with all its attached organs, we must infer that they had a much softer membraneous covering and consistency, but we can by no means infer that those parts did not exist. This view of the subject is rendered more probable, when we observe the same quality of the abdominal surface and its organs in still existing organic bodies which are similar to tlie Trilobites ; indeed, a more particular comparison of the existing Trilobite remains with the shells of such living animals raises our assumption to a positive certainty, since we also recognize the greatest similarity in the latter. An accurate knowledge of the shell of the Trilobites is, therefore, the first and most important requirement for the observer. 14 VISIBLE STRUCTURE SECTION III. My observations on this subject must be preceded by the explanation, that the real shell has by no means been preserved in all the Trilobites, but that a great part of their remains consists merely of impressions from the shell. This is the case in all the Trilobites of the grauwacke and of the clayslate, therefore particularly in the OJenida ; undoubted remains of the shell itself are first found in the specimens from the alum slate, and the same is more or less perfectly preserved in most of the individuals inclosed in the transition limestone.* In individuals from this rock, especially in such as are found as loose stones in many localities of Northern Germany, and which are already perfectly freed from the limestone that formerly surrounded them, we see most distinctly that the shell con- sisted of two layers, of which the external one extended itself over the lower, thicker, darker layer as a very thin, and generally clear coloured, coat. This fine coat is closely covered with small uneven tubercles, or is granulated on its whole external surface, and has therefore quite the appearance of the horny shell of our river crawfish, especially at the claws. These granu- lations were so slight over most parts of the body, that they left no trace at all in the second or lower layer of the shell ; but their presence in the more elevated portions, as, for instance, in the arched anterior portion of the head, and on the rings of the body, betrays itself, even when the upper membrane is wanting, by light but larger tubercles, which cover these spots. They attain their greatest development in the CaJijinene variolaris, which derives its name from them, but they are likewise not wanting in the Dudley Trilobites {Calymene Bhnnenbaclni). It is only in these, and in the smaller specimens (var. jmJcheUa), that I have hitherto been able to observe the external layer with its granulations in a well-preserved state ; the upper layer is almost always wanting in the granulated species of Pliacops ; the general granu- lation, therefore, can only be inferred from the existence of those larger granulations of the lower layer of the shell. The granulated surface, however, seems to have been a general quality of the group in the two genera Cali/meiie and Pliacops, and seems to belong to all their species. Most published figures of /"//«fo/)« confirm this opinion; the granulation in the genus Calymene has generally been overlooked, because it is here much finer and slighter, and because it is usually only recognized on the upper membrane itself. If, however, the second layer of the shell has likewise been cast ofi', and if the impression of the interior of the shell of the Trilobite only is existing, those indistinct coarser traces of granulation are, as a matter of course, also wanting, and the surface appears to be smooth. This is not only veryfrequently the case with regard to Calymene Blnmenhackii , but also very often with Pliacops latifrons, and with regard to the latter has given rise to the enumeration of several species (C. latifrons, and C. Schlotheimii, Bronn). P. iwofuherans, and all the species of this genus which are described as smooth, seem to originate from those individuals the membranes of which have been cast off. * These remarks ^Tere intended, no doubt, bj^ the author, to refer chiefly to the distribution of Trilobites in the rocks in his own neighbourhood. The actual shell of these animals is found frequently in the Siliu'ian limestones in England, and sometimes in the Caradoc sandstone, the oldest rock in ^vhich they appear. The shell is found also in the Devonian and carboniferous limestones. — Eng. Ed. OP THE TRILOBITES. 15 SECTION IV. The upper membrane just described seems only to be a peculiarity occurring in the genera mentioned, and of some others {Brontius, Odontopleura, Jloiiialoiiotus), but wanting in most of the Trilobites. Not even the slightest trace of a more delicate layer, capable of being thrown off, can ever be discovered on the surface of the shell of perfectly well-preserved remains of the genera Asapliiis and Illanus, indicating a different quality of the horny covering of these genera. In individuals whose external surface is in some places not at all injured, I perceive, on the other hand, fine deeply cut lines, which run pretty much in the same manner as the furrows in the palm of the human hand, but are situated more remote from one another, and have fine punctured dots between them. I observed this character of the surface-membrane in Calymene and Phacops, but most distinctly in Asaphus expanms, var. cornigerus, upon the arched anterior portion of the head, and at the most elevated parts of the rings of the body, and often exactly at those points where the granulation is most perfect ; on the other hand, I noticed those fine points in greater number and in a closer position on the lateral portions of the cephalic shield, on the lateral lobes of the rings of the body, and on the caudal shield, but in those places they are only single, coarse, rather elevated diagonal lines, which, however, are distributed in a tolerably symmetrical manner. This formation likewise meets with its analogue in living Crustacea, and may be found in the thorax of the lobster, particularly as regards the punctures. These granulations and punctures, however, only exist on that surface of the shell which is at the superior side of the animal, for the inferior surface, as far it has been preserved, has a diS'erent structure. It was likewise covered by a peculiar, but always thinner, horny membrane, which, however, gradually became more delicate the nearer it approached the middle, being everywhere separated from the upper side of the shield by a layer of muscle, and itself consisting of a softer structure. These statements may be verified by observations ; and, as one reason in support of them, I may state that we always find in the remains of Trilobites, in which both layers of the shell are existing, that there is a layer of rock between them, which indicates their distance from one another. As another reason, we may state that we observe at once the thickness of the petrified shell by such layer of stone, and perceive that the lower layer is thinner than the upper. For the better understanding of these proportions, I beg to refer my readers to the illustration of the large Asapjhts shield, which I have given in Plate V, Fig. 4. This shield is still covered on its left side by its old petrified shell, furnished with its natural surface, and therefore only exhibits a tolerably well-defined system of parallel striae at that part of the anterior margin which was overlapped by the lateral lobes of the last thoracic ring. A sharp broken edge, which at first runs along the whole length of the middle of the abdomen, and then turns towards the left, indicates the limit of the broken shell. That which is still visible towards the right is only the impression of the shell on that part of tlie stone which penetrated into the shield of the abdomen. From this part, however, a considerable piece is broken off at the posterior margin, and there is not only visible a part of the lower shell, but also its impres- sion into the stone situate beneath it, at those points where the shell itself is wanting. This accidental quality of the shield proves distinctly that the lower surface of the 16 VISIBLE STRUCTURE shell is furnished with fine parallel lines, as in the covered part of the upper surface at the anterior margin ; that it consists of a horny membrane, thinner than the latter ; and that the distance of the two membranes from each other was much greater in an angle of the lower layer than at the other parts of the whole shield, greater indeed even than at the end of the real abdomen, the lancet-formed point of which — at least in this case — seems to have been flat. For there seems to me no reason for supposing that this part was flattened by external force, and was originally aixhed downwards, since the parallel angle of the lower side is perfectly preserved, and not flattened, which certainly would have been the case if the whole shield had sufi^ercd considerable pressure. The lateral lobes of the joints of the body and the whole cephalic shield are formed also like this shield of the abdomen. Thus we may most distinctly convince ourselves, from many fragmentary specimens, that the entire lower surface of the shell of the head was covered in the neighbourhood of the anterior margin with such deeply cut parallel lines, giving that surface the appearance of a regular striation, the furrows of which run parallel with the circumference. The interior as well as the exterior surface of the lateral lobes is formed in a somewhat similar manner, though not entirely so, as far as the latter is covered by the preceding lobe. On this lobe, however, the lines run lengthwise, are not so deep, are frequently furcated, and are in general not so regular as at the cephalic and caudal shield. I have nowhere been able to perceive the dots between these lines of the lower surface, which are situated between them at the upper surface, and which even occur at many places by themselves, without the lines ; they are here, as they are generally, wanting as the granulations at the lower surface of the species of Calymene and PJiacops, in which, however, the cross striae described are as generally found as they are in Asaphus and lllanus. We have not, however, so many opportunities of observing them, since most specimens of these genera, and indeed always the most beautiful ones, are rolled up, so that we are unable to observe any of the parts of the lower surface. This is all that I have been able to ascertain with certainty as to the nature of the shell of the Trilobites. I suppose the same structure to be existing in the Olenides as in Asaphus, at least I have been able to convince myself of a similar striation of the lower surface. Genker has also observed the same, and indicated it in his figures, for instance, in Table V, Fig. c d. SECTION V. Proceeding to the subject of the divisions of the body, and commencing with the consideration of the head as the first, we shall soon observe that this part is encased in a great parabolical semicircular lunate shield {scidiim capitis, cephalic shield), in which the head itself only occupies the central, and, therefore, the more highly arched part. This central part, the head itself, which 1 shall henceforth call head-tubercle {Kopfbxckel — glabella, according to Dalraan), is very distinctly characterized by a furrow round it of greater or lesser depth, is always rather longer than broad, generally broader and thicker at the anterior part, and is there also more highly arched and more strongly projecting. In many instances impressions exhibit themselves on the whole elevation, which proceed from the furrow surrounding it, and which, more or less, penetrate into the head-tubercle, some- OF THE TRILOBITES. 17 times even (as in Pamdod'iilcs and Ohnm) becoming complete cross furrows.* There are at tlie utmost tliree such furrows at eacli side, separating lobes from the lateral margin of the head, which are partly even, partly uneven, and in the latter case form the broader lobes either on the posterior part [Cali/mene), or on the anterior part [PJiacops). In other cases they are entirely wanting {Illa-nus), or are only indicated as slight depressions of the margin of the head {AsojjJims). Next to the central head-tubercle is seen the cephalic shield, which, however, generally is not quite flat, but likewise slightly arched, so that it declines more or less towards the circumference, thereby forming a cavity beneath it. Of its two margins the anterior is always more strongly curved than the posterior, the former frequently representing a very pointed parabola or hyperbola [Isotclrs), whilst the latter only exhibits a circular arch. The latter becomes deeper in proportion to the greater or lesser projection of the frequently long pointed lateral angles. The margin of this cephalic shield is either extended flatly {Amplius, Isoicles), or has a distinctly protuberant margin ; in the latter case either having an acute angle [Calijmene) or being rounded off [Phacops). The central portion of the posterior margin, at the part where it covers the first ring of the body, usually projects in a thickened, swollen, and even ring-like form {Jscqj/iuis) ; the furrow-deposit, however, which I shall call neck-collar {Gelenkwulsf, sulcus verticalis of Dalman), also usually disappears towards both sides so rapidly, that it scarcely extends bc3'ond the middle of the lateral lobes. In other numerous cases the collar extends quite as prominently in the middle of the posterior margin, but is distinctly separated from the central part, as far as the lateral angles, then passes round, surrounding the latter, and is continued along the entire anterior margin, frequently appearing there still higher, stronger, and more distinct than at the posterior margin {Calymene, Phacops). All these differences are pretty constant charac- teristics of genera or groups, and therefore demand an attentive observation ; this particularly has reference to the lateral impressions of the head- tubercles, since these are probably not mere ornaments, but may perhaps have reference to the organization of the mouth. We usually, indeed, find swellings and protuberances on those localities of the shell of the Articulata where strong muscles are attached internally, and the elevations situated between the transverse impressions may, therefore, probably originate from such attachments of the tracheal muscles ; so that from their number we might infer the number of gills. It certainly seems opposed to this conjecture that the organization of the internal part of the mouth in the case of other natural groups of Articulata is generally uniform, while in the Trilobites the impressions on the head are generally very different. The force of this objection, however, may be diminished by assuming that the forms in which we find defective impressions were characterised either by a greater thickness of the shell, or by a slighter development of the muscles, so that the traces of the impressions of the muscles were rendered less distinct, or were entirely effaced. And, in fact, the genera in which such impressions are wanting {Illanus, Asajjhus, and some species of Phacops) seem to possess a * If we place confidence in this characteristic of many perfectly preserved Olenvulcs, namely, that the cross furrows of tlie head-tubercle are complete, and if we may consider it as a general family characteristic, several forms would belong to th;m which have hitherto only been observed in imperfect specimens. According to this, we should particularly have to enumerate Trilobites Sternbergii (Table III, Fig. 7), which, in point of the cephalic stnictiire, is most nearly related to Olenus scaraboeoides, and Triarf/i/us Breki as both belonging to the Oleneides. 3 18 VISIBLE STRUCTURE very powerful and thick shell, whilst in the Oleneides, which always present impressions, the shell was decidedly thinner, and consequently became entirely lost. The few existing positive facts, however, do not permit us to determine this point with certainty, and we must, therefore, content ourselves with having pointed out the possibility of one or the other mode of organization. SECTION VI. The number, position, and structure of the eyes can be ascertained with much more certainty, and are therefore comparatively well known. There are, however, still many deficiencies in the knowledge existing on these points, which is the more surprising since we are enabled to make a perfect representation of them from actual observation. In all those Trilobites the eyes of which can be distinctly recognized, we see them in the shape of more or less considerable prominences at the sides of the head, nearly on the centre of the lateral portion of the shield, projecting from the latter. They are here seen as portions of a spherical or parabolic surface, under a semicircular projection (the cover of the eye, or of the horny covering of the head), which projection is formed by the sutura tempo- ralis, (of which a description will be found subsequently,) and in reality they fill out a chasm that is situated at this locality between the two opposite margins of the suture. The eyes project in the shape of a half-cone, flattened on the upper part, if this vacuity is large ; if small, it forms a lunate protuberance, which is so slight in some species that it scarcely rises above the contiguous surface of the head. Such Trilobites have been considered as blind ; and with regard to Oleums, which genus possesses the structure described, it is given as a generic character. The eyes of the lUamiis are in the shape of a moderately arched, lunate swelling ; in Ascqjhus, CaJijmene, and Phacops, they appear as more highly elevated tubercles or hemispheres. Whilst the external surface of the eyes in the other genera is per- fectly smooth, and even more so than the neighbouring horny covering, there appear in PJiacops, instead of these, small hemispherical elevations distributed over the entire surface in regular order, the small interstices shaping themselves into protuberantly swollen in- cisures of the hemispheres. Owing to this, the eyes of the Trilobites ai'e usually represented as being formed on two different types, assigning to the former a smooth, to the latter a facetted cornea. This view, which is entertained by all fomner observers, I must consider as decidedly incorrect : first, because there is not a single existing family of Articulata in which the eyes are formed according to two different types; and, secondly, because the character of the facettes in Plutcops is quite different from the mode of formation pre- dominating among the Articulata with a facetted cornea. I am rather of opinion that all Trilobites possessed compound eyes with a smooth cornea, and that the latter has merely been lost in those genera in which facettes are perceived. In addition to the two reasons mentioned, I am further justified in this assumption by the fact that the cornea of most of the Trilobites is really smooth, and that the structure of the eyes of those species, to which a facetted cornea is attributed, is in every respect such as it would be if their eyes possessed a simple, smooth cornea, which was subsequently lost. This, therefore, seems to be the proper place to explain more particularly the structure of the compound eyes with a simple, smooth cornea. OF THE TRILOBITES. 19 SECTION VII. Eight years have ah'cady elapsed since I particularly described the type of this form of the eye (to which Midler* first directed attention), in its most important living representative, the Branchipus sta(jiiaUs, and I then showed that the eye of this animal consists of four suc- cessive layers of different kinds. The external layer is a smooth, homogeneous, transparent cornea. Beneath it lies a facetted membrane, which, seated in a clear substance, contains rather darker, firmer, circular, apertures, of equal size, and regularly distributed in such a manner that every ring is surrounded by six others, at equal distances from each other. The third layer of the eye consists of egg-shaped, transparent, very hard lenses, each of which is situated behind one of the little window-like apertures described, resting upon the surface of the latter with its flatter extremity, and raising this a little with that convex surface. The fourth layer consists of an oblong, club-shaped, crystalline body, which encircles with its upper thicker end the more pointed end of the egg-shaped lens, and is surrounded by a delicate membrane. A continuation of this membrane also overspreads the lens, and attaches itself to the thickened margin of the little aperture before each lens. Behind the crystalline body there then follows the dark pigment as the principal mass of the whole eye, through which the fibres of the optic nerves extend themselves to the respective ocelli, resting on the basis of the crystalline bodies, as their sheaths pass into the sheaths of the crystalline body, and the lenses, and through those sheaths likewise attach themselves to the facetted second membrane, f This representation of the eye,;}: which is perfectly applicable to. the Trilobites with a smooth cornea, shows us that the loss of the external smooth cornea immediately occasions the projection of a facetted cornea, § and we therefore only need assume with respect to Phacops that their cornea must have been more destructible than that of the other Trilobites, in order to explain their facetted character. Sufficient reasons are also in this respect furnished to us by the propor- tions of organization in existing genera. The study of all those Crustacea, for instance, that are furnished with a smooth cornea, and they are only found in Articulata of that description, proves to us the important fact, that the number of the separate ocelh does not at all depend on the size of the whole eye, since they merely become more minute as the eye diminishes, their absolute number in that case sometimes actually becoming greatei'. The cornea becomes thinner in proportion to the increased size of the eye, and thicker as the eye is smaller; so that very large eyes with a smooth cornea possess a thin cornca,|| very small ones, on the other hand, a thicker and more compact cornea. Now Phacop.'s * MüUer's Archiv for 18.35, pp. 529, 613. t Vide Table YI, Fig. 4, and its explauatiou. X Vide Quenstcdt in AViegmaun's Aj-cliiv für Nat. Gesch., series 1837, i, 340 ; where the structure of the eye of the Trilobites with a smooth horny membrane is correctly recognized and described. § In .Toll. ]Müller's description, which we ha\e before alluded to, the facetted membrane and glassy substance is not mentioned. AVe need not, however, infer from this that they ai-e wanting in some eyes ; they have only escaped the attention of the observer at this first investigation, and are cer- tainly met with in all the Articulata Avitli the described form of eyes. II Compare in these respects, for instance, the genera Branchipus and Apus, or Polyphemus and Daphnia. 20 VISIBLE STRUCTURE has, relatively speaking, the largest e)'es among the Triloliites, consequently also the largest lenses and the thinnest cornea : a fact which is decidedly cstalilishcd, and suSiciently explains the absence of a smooth appearance in the eyes of this genus.* The truth of this view is, however, still further supported by the circumstance that the facettes in all the Crustacea, and in most of the Articulata with a facetted cornea, are perfectly contiguous, leave no open in- terstices, and individually are much less convex than in Phacops. The eye of the latter genus, if it possessed a facetted cornea, could only be compared with the eyes of some nocturnal insects, for instance, of the Redavies, or of some of the parasites, such as the RMpUdoptera, in which the facettes are larger, more strongly arched, and situated more remotely from each other, or it might be explained as an aggregate of simple eyes ; against which conjecture, however, there would always be the fact of their peculiar circumscribed form. Aggregates of simple eyes, as they occur in Mjnopock, and in some of the hopods, consist however always of a smaller number of ocelli, whilst the number found in Phacojjs is very considerable.f Thus I beheve I have proved the correctness of my assertion, that this genus, in common with all other Trilobites, possessed a smooth cornea. Before concluding this part of the subject I might, however, refer to the frequent actual deficiency of the cornea and lenses in Cahjmene BlumenhacJiii, and quote the absence of the latter, which naturally arose from the small size, as an additional argument in favour of my view. These parts of the eye were, indeed, so small in this instance, and their coats so tender, that they could not have been petrified after the loss of the protective horny cornea membrane. SECTION VIII. We shall now return to the already mQwiwweA liiiea facinlis, or sidiira temporalis, and trace the principal variations of these lines. There can certainly be no doubt that the possession of a temporal suture is a common character of all Trilobites ; it exists equally in Paradoxides and Olenus. It is generally first recognized at the anterior margin of the common cephalic shield, at a moderate distance from its centre, so that both lines remain at a rather greater distance from each other than the transverse diameter of the cephalic protuberance at its broadest part. But in Ogijqia, Phacops, Homalonoins, and AsapJuis, the temporal sutures extend themselves at the anterior margin to the extreme point of the cephalic shield, and here unite, forming an arch or angle. In the other genera they are curved on the lower side, round the anterior margin of the head, and terminate in the margin which separates the cephalic shield from the mouth. Converging a little towards the posterior part, they now approach from the margin to the protuberance, as far as the region where the eyes are situate, here they describe the outward curved lobe over the eye (operculum oculi) already alluded to, and again extend behind it rather more towards the outer part to reach the margin of the cephalic shield at a second point. * Since the publication of tlie German edition, I have observed in the eyes of Phacops mucronatus, from Bohemia, the globular spots hollowed out like a funnel, all regularly in the same manner ; a form impossible, I think, if the spots were coruese. t I counted 163 hemispheres of leuses in each C3'e of the Phacops arachnoides ; of Phacops mucronatus, on the other hand, 209; of Phacops lat'ijrons, only 90- 100. OF THE TRILOBITES. 21 Tlie part where this takes ph^ce is very differently situated, and is, in some cases, at the posterior part of the margin of the liead, but in otiiers, at the exterior part. Each g-enus has a certain point at which this takes place, and it is different in each. Paraclondex stands in this respect at one end of the series and Phacops at the other. The point of termination in Paradoxidcs is, for instance, situated much nearer to the raised margin of articulation or collar of the cephalic shield than to the lateral margin, and both extremities of the suture are only just as far removed from each other as the eyes are. The latter proportion exists also in Ulcenus, but owing to the great distances of the eyes from each other, the distance of the ends of the sutures from the central line is much greater than their distance from the lateral margin. In both these genera, however, the sutures posteriorly run parallel in the principal direction ; but they diverge in all others. This divergency is slightest in the species of Ogyyia and Ascqjhus and in Parado.vides gihboms, and Calymcne conciiina, which do not however belong to the genera the names of which they bear, and it is so great, that it extends beyond the centre of each lateral lobe of the posterior margin of the head ; in Calymene Blumenhachii, and in the other real species of the same genus, it increases to an im- mediate termination into the angle of the cephalic shield itself,* and in Phacops even passes over to the external margin of the cephalic shield, as Dalman has already illustrated this in Ph. sderops, his Cahpiiene sderojjs (Tab. Ill, Fig. 1, d). The two ends of the sutures in this case nearly describe single straight lines along their principal direction, and these lines are at right angles with the longitudinal dimension of the body, so that they are therefore removed by about 90° from the dii'ection observed in Paradoxides and Illanus, as well as from the other extreme. It is evident that so constant and regular a course must be particularly calculated to afford safe characteristics of genera. Besides this temporal suture, which is com- mon to all Trilobites, I have further observed a second real suture in the crust of the head, which has been overlooked by most authors.f It is only found in the genera Calymcne and IUcbiihs, immediately beneath the upper angle of the anterior rim, on that side of the latter which is turned downwards, and connects the two parts of the temporal Suture, which in their termi- nation incline somewhat inwards. It is, however, only to be detected in very well preserved specimens, but in such it can be seen quite distinctly, and in CaJymeiie it not only occurs in the granulated upper membrane already described, but it also exists in the second layer of the crust lying beneath the former. In all other genera, I could not discover any trace of this second suture, or sntnrn marginal is, and must therefore assume that it does not exist in these genera.;}: Indeed I find that we meet with three quite different types in the composition of the cephalic crust among the Trilobites, the principal differences of which consist in the circum- stance that this entire shell, as far as we know it, may consist of two, three, or four pieces. * The edges of the liearl are always short if the suture divides them, but (jften elongated into angular processes if the suture goes to the basal or external margin. These processes are only pro- ductious of the crust, and are soUd, without any hollow, so that they could not exist if the fossil were a crust, but only if the crust itself of the animal be petiified. Hence it is that individuals of the same species, as Phacops sclerops, occur some with long horny head-processes, and others without any. t It has been pointed out in Buckland's Fig. 3, Table XL VI, and INInrchison's Fig. 7, Table VII. X M. Emmerich, in his ' Dissertatio de Trilobitis,' p. 8, (Berolis, 1839, 8vo,) also speaks of two sutures at the cephalic shield, hut describes the temporal suture only more accurately; the second (quae partem inferiorem a superiore separat) he merely refers to in these words. I have nowhere seen it at the whole circumference of the cephalic shield. 22 VISIBLE STRUCTURE The temporal sutures in the first case, by no means pass over to the lower side of the cephalic shield, but continue at the anterior margin of it, and there meet together, so that both are only the different directions of one suture going towards the left and the right. This formation I observed in Oqi/f/ia, Pliacopfs, Amphits expanms, Wahl., and in all flat-headed species of this genus, as far as I have been able to investigate them. This transition takes place in the shape of an arch terminating near to the anterior margin in Amphus cxpaiisus, A. laviceps, and A. {Nilens) armadillo, as also in Oyyyla and Phacops; it takes place, however, in A. ramiceps, A. anpistifrons, and A. extemiatus, in a sharp, more or less pointed, angle. I could never recognize a suture proceeding from this point, which had divided the lower surface of the shell, v*^ith any degree of certainty ; Pander, however, has found such, and considered it as the line of separation of his side branchiae {vide Table IV, B, of his work). The entire cephalic shield of this pointed headed Ampjlnis likewise therefore only consists of three pieces, an upper internal one, which covers the cephalic pi'otuberance, and which I term central shield {scutum centrale), and two upper external ones, which at the same time pass over to and form the lower side, as far as we are acquainted with it. I call them margin shield {scuta marginalid), or temporal shields {scuta temporalin). In the second case the two temporal sutures extend themselves over the anterior margin of the head, and reach, separately, that lower margin of the cephalic shield which incloses the region of the mouth, and which I shall subsequently describe, separating it from the cephalic shield. The anterior end of the central shield in this case, therefore, also passes over to the lower side, and thus we have three shields of the head-crust, a simple central shield, and two margin shields. The Oleneides belong to this group. The central shield in these only occupies the central part of both margins, and the entire lateral portions complete tlie marginal shields. The two temporal sutures, in the third case, also terminate quite separately, reach exactly the angle of the head-crust at the posterior part, but are connected anteriorly beneath the protuberant margin of this crust by a transverse suture, which here separates a piece of the lower surface of the shell placed anteriorly to the region of the mouth, so that four pieces are thus formed, viz. a central shield, two marginal shields, and a shield situated in front of the mouth, which I term scutum rostrale, and the suture which separates it I also term sutura rostrcilis Such a structure may be met with in Cahjmene and IllcEnus* Such is the account I have to offer concerning these sutures of the head-crust ; I have only further to observe, that similar unions of the pieces of the crust, by means of sutures, can- not be traced in any of the existing Crustacea, but are only found in true insects of the present W'Orld ; they constitute, therefore, a most remarkable and important peculiarity of the Trilobitcs. We shall see subsequently that they do not occur again at any of the other segments or shields of the shell of the Trilobites. No satisfactory conjecture as to their purpose can indeed be hazarded without an accurate observation of living animals. Pander's opinion (p. 117), " that the connexion of the parts is perfectly dissolved by this suture," and that in the living state of the animal it had served for the purpose of removing the lateral shields from the central, and thus permitting a changeable distance of both from one another, at the option of the animal, can scarcely be founded on fact, for at the present day we by no means find * Professor Löven observed in the genus Trinucleus or Cryptolitlius a new and very different type marked by the course of the sutures, which I shall describe in giving the character of the genus. OF THE TRILOBITES, 23 so great a mobility in those Articulata, whose shell pieces are connected by sutures ; on the contrary, the mobility of the plates upon one another is always very slight, and a considerable distance of the margins of the suture from one another is impossible, if it were only because a soft membrane arises from the internal margin of the sutures, connecting intimately both tlie suture margins. Owing to this, the elements of the skeleton of the liighest Articulata can at the utmost be only bent towards each other, never being separated from one another to any considerable extent. The facial suture of the Trilobitcs probably likewise admitted of such an easy bending of the lateral shields towards the central shield, and might be intended for the purpose of arching the space beneath the cephalic shield somewhat more during the contraction, so that the requisite height might be gained for the feet, which were then hidden beneath the cephalic and caudal shields. Indeed the intimate union of the lateral lobes of the segment of the trunk in one section at the posterior angle of the scuta temporalia testifies that the object was to conceal all the lower parts as much as possible beneath the head-crust during the rolling up of the Trilobitcs.* Such a section is found at the lower side of the angle alluded to, immediately behind the external margin ; it is particularly distinct in the genera Asapltus and lUcemm, visibly sharpens the margin, which before that point is thick, broad, and rounded off, and thereby causes a cavity in the margin itself, running parallel with the acute angle, the cavity being intended for the reception of the lower end of the last lateral lobe, situated before the caudal shield, when the Trilobite was rolled up. The axis, around which the animal doubles itself, is situated very near to the locality where the two furrows, which run parallel with the lateral and posterior margin of the scuta temporalia, meet together before the posterior angle, and the lowest ends of the lateral lobes of the joints of the trunk also usually conceal themselves to that extent beneath the cephalic shield. The excavation behind the margin before described serves, therefore, for their reception, and indicates that a Trilobite possessing it had the power of doubling itself together. On the other hand, however, it will not do very well to infer from the absence of the section, that such a Trilobite could not have rolled itself up. I certainly have always looked in vain for it in all the Oleneides, nor have I ever perceived any traces of the capability of doubling themselves in these Trilobitcs ; but I could quite as little discover that section in Phacops and Calijmeno. SECTION IX. We have now still to investigate those remains of the existing parts of the cephalic crust, which have been observed on its lower surface behind the margin, and evidently in front of the mouth. The first who observed this region of the head in Olenus Tessini, Dalm., was Wahlenberg ; he took it, however, for the impression of the upper side of another species, and described it as Entomostracites buccphalus (p. 37, 10, Table I, Fig. 6, of his work). Subsequent to him, the same region was observed and represented by Stokes in Isoteles gigas (his AsupJi. plufi/ccj)Jialus), and by Eichwaldt in Asaph us eapansus, Wahl, (his CryjAonymus Panderi), but they were not correctly observed by them. The same may be said of Pander, > Tabic ^'I, Fig. 8, // 24 VISIBLE STRUCTURE whose representation is certainly more particular, but without any correct interpretation of what these parts really are.* Sars was the first who recognized them for what they are, namely, for the lower protuberance of the head before the mouth, and described them as such in the genera Illa'uun and xhaphis ('Isis,' 1835, p. 340, Table IX). I myself have only hitherto observed this region pei'fectly in Phacnps and Parado^rides ; in Amphus and Illanxs, however, I have discovered them so distinctly, that I cannot doubt their existence, and the correctness of those former representations. The great similarity in the figures of the four authors, who, however, were not acquainted with the works of their predecessors, also speaks in favour of this opinion. The following is the structure observed. A moderately arched protuberance, which in size and circumference corresponds pretty nearly with the most anterior portion of the head on the ujjper side, exhibits itself immediately behind the thickened anterior margin of the cephalic shield, that part which Pander terms lateral gill. It was intimately connected with the anterior margin of the head, and has certainly not been moveable at pleasure, as Pander supposes, in consequence of its isolated position in some individuals. {Vide Table IV, B, Figs. 3, 4, of his w^ork.) From the anterior part it extends itself with a pair of lateral lobes, which are more or less distinctly separated from the central lobe, along the margin indicated, towards the external part, and there terminates in a long, more pointed, less arched projection. Towards the posterior part in Puradoxides there is a rather protuberant margin, curved outwards, and before it a considerable oblique excavation. This margin in Asaplms and Illceiuis, on the other hand, is deeply notched and strongly double lobed. In all three are exhibited on the whole surface the same indented concentric lines, which cover the lower surface of all parts of the shell. Sars certainly represented such lines only on the lateral lobes, but I have found them everywhere on the whole surface in P. bohemiciis {Enf. hiicrpJialiis, Wahl.), but certainly slighter in the centre, and therefore I suppose that Sars must have overlooked them. I have represented this region of P. boliemiciis on Table I, Fig. 7, and have availed myself of ■Sars' figures of Asaplms in my drawing, Table VI, Fig. 8. There can now scarcely be a doubt that this region is the ordinary enlargement before the mouth, which we perceive in the Plii/llojiodes, and which is usually called hyposioma. This certainly testifies as decidedly in favour of the affinity of the two groups, as it negatives the affinity with the Isopudes. But of this hereafter. SECTION X. The tliornx or bodu of the Trilobites, to the description of which we now proceed, consists of a number of homogeneous rings, of which every one likewise possesses a horny crust. The latter has, as on the cephalic and caudal shield, lateral freely projecting lobes {pleurcB) at each ring, which are readily distinguished by their flattened and ge- nerally incurved form, from the uniformly arched semi-cylindrical body. These lateral * Pander supposed that these, as ^ell as the lateral margins of the head that are turned over, were gills ; and terms the hitter lateral gills, the central swelling bcliind the anterior margin central or lower gill, and even believes that there were respiratory organs iu the swelling before the mouth. [Vide pp. 134 and 128 of his work.) OF THE TRILOBITES. 25 lobes consisted (exactly as in the already described flattened extensions of the cephalic and caudal shield) of two layers, between which there was a thin layer of the substance of the body, and these were, on the external, open, upper surface, partly smooth, partly granulated ; but on the lower hidden surface furnished with parallel striee. This is distinctly seen in the fragments of Amplius and IUwiiks, in which both coverings of the lateral lobes arc generally preserved, showing that the intermediate layer at the upper and internal parts of the lateral lobes was thicker than at the lower part, (which is curved forwards,) where each lobe terminated in an acute angle towards the external and upper part. On the other hand, it formed a broader rounded facing. If I appreciate these impressions correctly, I should say that the internal horizontal part of each lateral lobe must have been in immediate connexion with its neighbour, and that this whole region of the body has participated in the protection of the fleshy muscular layer, situated beneath the arched central part, or may even have been partly the support of this muscular portion. This is probable, since in all the specimens, even those that are rolled up, these regions of the lateral lobes are not projected one al)ove another, but are at the usual distance from each other ; and I think I can perceive a kind of articulation in the anterior angle of each posterior ring, ■where the external part of the lateral lobes bends downwards. Such an articulation certainly exists at the place where the central arched part of each ring meets the lateral lobes, not, however, between this part and its lateral lobe, but between the central arched body rings themselves. At this spot, indeed, may be observed a strong hemispherical articulated head, immediately before the open posterior margin of the ring at its lower surface ; and this head fits into an articular cavity, formed to fit it in the succeeding ring. The latter exists at the anterior margin of the caudal shield, and is distinctly represented in Table V, Fig. 4. The first pair of articular processes occurs, however, at the posterior margin of the cephalic shield, and thus each segment has a pair of articular cavities on its upper side anteriorly, at the junction of all the rings with the preceding covered margin ; and on the other hand, at its lower free side, which partially projects over the succeeding ring, it has a pair of hemispherical articular processes. These and the cavities may be very distinctly recognized in the larger specimens of the species of Phacops, whose horny coat has been lost ; the fractured «irticular prominences being usually still found in the articular cavities beneath them. There can also be no doubt, from the analogy of living Articulata, that besides this a soft articular membrane connected the margins of the rings, situated opposite to each other ; but in all other respects, each separate ring was complete in itself, its lateral lobes being immediate continuations of the central arched principal portion, and nowhere connected with the latter by means of sutures. It is true indeed that deep impressions are found at the sides of the thorax in well-preserved specimens of Ogyyia Buchn and Conocev/iahts Sitheri, separating the latei'al lobes of each individual ring from its axis ; but I should not be inclined to look upon these as sutures, which Emmerich declares them to be, because nothing of the kind is found in the other Trilobites ; and there are no apparent means b)' which these lobes could have been moved (as their mode of insertion indicates that they might have been), since they could only have had a very slight muscular layer on account of the thinness of the lateral lobes. I believe, therefore, that the suture-like furrow alluded to does not indicate a suture, but originates from an acute angle, which projected here at the internal surface of the crust, between the 4 26 VISIBLE STRUCTURE axis and lateral lobes ; for, considering the entire absence of remains of the crust itself, there can be no question that in the impressions of both species we see the impression of the internal surface of the shell. As little can I agree with Emmerich, who adopts the views of Audouin, that the lateral lobes consisted of two pieces, which correspond with the episternon and epimeron in the thorax of insects. There is not only no reason whatever for such a conjecture, but a decisive argument can be brought against it by referring to the fact, that the plates alluded to in insects are always portions of the crust, which encases the axis itself; while here they would appear as lateral projections, without forming part of the covering of the axis. Where there are no especial parts of the skeleton at each separate ring, as is the case with respect to the Trilobites, those names should not be applied which refer exclusively to such particular parts of the skeleton ; nor should they even be made use of in the way of analogy if they were introduced to describe parts differently situated, for such a mode of proceeding will cause the utmost confusion.* In fact, I must repeat that the lateral lobes are nothing more than lateral continuations of the crust covering the rings of the body, that they are incapable of independent motion, and that they serve no other purpose than that of protecting the delicately constructed feet situated beneath them. On this subject I shall proceed to enlarge in the following chapter, and then endeavour to reproduce the absent organs of the Trilobites from the analogy of living forms of Crustacea ; but it still remains to be mentioned witli regard to the central parts of the body, (tlie real body rings,) that each generally consists of two semicircular protuberances, situated one behind another, of which the anterior and smaller one is hidden beneath the projecting margin of the preceding ring when the body is in a stretched position, but which can be very distinctly seen when the body is curved or doubled together. At the end of the furrow, which separates the two protuberances, there is seen at each side the articular cavity, which is nearly circular in the species of Fhacops and Cali/me»e, and rather transverse in Asaphtis and Illcenus ; concerning the use of this I have already given the necessary information. We miss it entirely in all species and fragments deficient in the horny shell, since both parts, that is, the articulating process and the corresponding articular cavity, merely belong to the horny coverings. The transverse furrow of the central body, by which the anterior protuberance of each ring is separated from the posterior one, in most cases partially extends itself to the lateral lobes, and only disappears at the place where the latter bend themselves downwards by approaching to the posterior margin of the lobe, and * Audouin, in his well-known work on the skeleton of insects, (Annal. des Scienc. Natur., Prem. Ser., torn, i, 1824,) calls that part of the skeleton epimeron, which is situated between the freely move- able paunch (?) and the back plate ; episternon, on the other hand, he terms that part of the skeleton situated between the sternum itself and the back plate. Among the Trilobites, we find the only instance of these divisions of the external skeleton into separate pieces, in the head ; in all the other parts of the body there is nothing of the kind. This circumstance is a most remarkable one ; and it is without any an.alogy in living Crustacea, the shell of which always forms a continuation at the iu- di\idual rings, and never consists of separated pieces, connected by sutures, not even when it distinctly covers several rings. Dalman has already recognized and publislicd (Palaead. p. 13) an account of this exception from the general rule, that the skeleton parts of living Crustacea never have sutures ; and I must once more particularly enumerate it as a most singular character of the Trilobites, although at the same time it is necessary to observe that the peculiarity which distinguishes the head-crust of these animals does not appear in the other rings of the crust. OF TIIH TRILOBITES. 27 passing over into the anterior angle of the arched margin of the h)he. I doubt very much whether the presence of this furrow on the lateral lobes is of any material importance in the organization of the Triiobites in ^Yhieh it occurs, for if this were the case, it could not be entirely wanting in some genera, for instance, in Ilhcnm ; and I rather consider it as a secondary matter, caused by the presence of the transverse furrow on the central rings themselves, and thus continued to the lateral lobes. This view can be supported by the structure of Illaiius, in which the transverse furrow is as much wanting on the central principal ring as on the lateral lobes, and which therefore have a much flatter, and more uniformly arched back than the other species, the back rings being always individually very strongly arched. The organization of the abdomen of the Macmra furnishes among the living Crustacea an exact counterpart to the usual Trilobitc structure with furrowed rings ; while the organization of the thorax of the Amph'qwdcs and Iwpode-s, on the other hand, represents the form existing in lUcenus. Both modes of formation, however, admit the power of rolling up, both by the Triiobites and by their living analogues referred to. SECTION XI. The number of rings, of which the thorax consists, is a circumstance of great import- ance. The number may be readily ascertained in those genera which have a large caudal shield, but with greater difficulty in those where the body terminates in a very small shield, in which only four rings are contained. The question arises here, whether the thorax can really be assumed as extending to this shield, or whether, judging from the analogy of living forms, a portion of the rings before the terminating shield does not belong to the abdomen, the real boundary of the latter being determined by the position of the sexual opening, as in Apis. Nothing of course can be decided in this respect, owing to the absence of all soft parts ; and we have therefore no alternative but to consider the thorax in the Triiobites as extending to the simple caudal shield, and the rings contained in the latter as the abdomen. Assuming then this to be the case, we find a very great difference in the number of the thoracic rings. The smallest number appears to be five ;* Sarsf at least asserts that he saw no more in Ampyx ro.strafi/s ; whilst, according to Dalman, Ampi/x nasufii« possesses six rings ; and since I am not aware of any authenticated case in which different numerical proportions of the rings occur in the same genus, I must assume that the first number is incorrect. The latter number is also found in Crijptoliihts, Green ; and Trinucleus, Murch. I have hitherto nowhere been able to perceive seven distinct rings ; and although this number is stated by some authors as existing in Of/i/yin, the number of eight stated by others seems to con- tradict the correctness of this calculation. Eight articulations are possessed by all species * Dr. Beyrich, in his 'Treatise on some Bohemian Triiobites' (Berlin, 1815, 4to), describes a perfectly preserved specimen of Battus integer with two body rings. This number therefore was the smallest. t ' Isis,' 1835, p. 335. 28 VISIBLE STRUCTURE of the genus Amplim in their entire extent, also by Arr/es and Odontophura. Dalman enu- merates nine rings in lUcenm cettlrofiis, but one ring might perhaps have escaped the attention of the observer, since they are so remarkably small in this species. With perfect certainty, I only find this number in Archcgonm (De Koninck's PhiUipsia). The true Illani have ten rino-s. Dalman's Cahjmene concinna possess the same number, and if on that account only cannot belong to Cahjmene, nor can it indeed be referred to Amplim, among which Emmerich places it. The species of Phacops have eleven rings, EUipsocephalus twelve, Cali/mene thirteen, Oleims gibbosus and Conocephalus fourteen, Olenus spinulosus sixteen, and Parado.cides bohemiciis has twenty rings. This seems to be the highest number of rings existing. SECTION XII. The abdominal or caudal shield {scutum canda; ^.pggidlim), which we have next to describe, has already been mentioned as an extension of the coverings of the real abdomen, analogous to the cephalic shield, and has been exhibited as consisting of two layers, of which the upper possesses the same quality as the rest of the upper surface of the shell, while the latter more tender layer is marked with lines on its open surface in a similar manner. Between both of these, however, a thicker layer of the substance of the body must have existed. There remains therefore now only to treat of the axis of the shield, the true abdomen, in which we may also usually observe an articulation, although the rings are never so distinctly and regularly disposed as in the thorax. With respect to their distinctness, three stages may be enumerated, which may be termed the stage of perfect distinctness, of the indication, and of the deficiency of rings. The genera Tmiudeus, Ogygia, Calymene, Phacops, JEonia, exhibit perfectly distinct rings. Very distinct rings are also to be observed in Olenus gibbosus. The arch of the ring itself in this case is continued to the lateral portions of the caudal shield, but the number of ribs is usually less by one or two than the number of rings in the" axis ; at least, I have counted only seven ribs in Phacops latifrons, while there are eight, or even nine rings in the tail, of which the last two are certainly very small, and merge into each other. Calgmene Blumenbackii has always five ribs at the caudal shield, but seven distinct articulations in the tail itself. In Ogggia Bitcliii I have counted eleven ribs at each side of the caudal shield, but twelve rings at the tail itself, of which the last has a long oval shape, and in all probability consists of several articulations. Phacops caudatus has at each side seven I'ibs divided by a groove, and thirteen distinct articulations, besides an oval terminal articulation, which may be considered as a union of several articulations ; Phacops Hausmanni, finally, has most of all, namely, nineteen to twenty-one in the axis, and thirteen to fifteen grooved ribs at each side. The terminal articulation of all the Trilobites is of a similar nature as described, and therefore probably only not articulated at the upper part, because the thick crust prevents the ring from becoming distinctly visible. In Moni a {Gerastos Goldf.) I have counted seven very distinct articulations in the axis, but I have not perceived any ribs at the side of the caudal shield ; in Olenus gibbosus, on the other hand, six rings in the axis, and five on the shield, may with certainty be recognized. OF TUb; TRlLOlUTliS. 29 Asaphiis c.vpa/isia s. conii/jeruii belongs to the form with iiulistiuct rings in the axis of the caudal shield ; I have counted in it six siiort articulations, and a long, oval, terminal articula- tion. In another imperfect one, I believe I recognize nine rings, and a shorter, almost circular, terminal ax'ticulation. In .-Isap/ius ti/ra/iiiiis, of which I know only the caudal shield, represented in Table V, Fig. 4, there are nine articulations, together with a long oval arti- culation. Indeed there seems to be an articulated axis, without elevated lateral ribs of the shield in most species of Asapkm, while the species referred to the group Isoteles might also belong to this, their ai'ticulation being merely very slight. I have seen no species of Amplw:^ without articulation at the axis. On the other hand, we miss the articulation entirely in Hheni/.s and Broutcs, so that both these genera are representatives of the third form of the caudal shield. The caudal shield corresponds almost completely in point of size and form with the cephalic shield in the genera AsapJms, Illanus, Ampi/x, and Trinudeus or CryptolUlms -, it is smaller in all other genera, because some of the body rings belonging to it in those genera have become isolated independent rings. Its size therefore decreases with the number of rings, and becomes smaller in the species of Phacops, Cal^mene, Paradoxides, Conocephalm, Ellipsocophnhm, and 0/eji//s, in the latter consisting only of one or two rings, ^onia or Gerastos, a genus which we have already mentioned as the t3'pe of a peculiar structure, is at the head of this series. A certain limit therefore seems to have been placed to the number of the body rings, and those of the abdomen seem to increase when those of the thorax decrease. Emmerich, indeed, has already considered this as the correct relation, but a more particular investigation does not confirm this view ; and, indeed, the fallacy of such a conjecture may be proved by the mere comparison of the species of Phacops among one anothei', inasmuch as they never possess more than eleven thoracic rings, and yet fluctuate between nine and twenty-one in the number of their al)dominal rings. The same thing is also seen in Calymene, but the limits of the series are not there so very dif- ferent from one another, but merely fluctuate between seven and eleven. {Cal. polyioma, according to Dalman.) It appears, however, that the rings of the thorax and abdomen together do not generally exceed the number of thirty, and that in many Trilobites the number in both divisions of the body does not amount to so man)% while the total number of rings is quite uncertain where the articulation at the abdomen cannot be recognized. For the rest, I have only to observe that the divisions at the axis of the head of Trilobites are likewise nothing more than indications of rings, but this can be easily reconciled with the view I have before expressed, namely, that they may be looked on as protuberances of the gill muscles situated beneath them, since as many body rings are always missed in all Crustacea as there are accessory pairs of gills at the head ; from which it is evident that every pair of gills is aflixed to a particular ring, the latter, however, losing its independency by its intimate junction with the head. Since also the number of lateral furrows of the head is never more than three, by which, however, there are never formed more than four pro- tuberances, we might assume as many gills in the Trilobites, and suppose that in all cases where these protuberances are wanting, and where the anterior lobe contains all the others within itself, one pair of the gills must have grown very large (this would be the first pair according to analogy), whilst the others have disappeared, although they have not perhaps 30 VISIBLE STRUCTURE OF THE TRILOBITES. been absolutely lost. But considerations of this kind belong to the following chapter, since I merely intended to describe the immediately recognizable structure in the present chapter, and this I believe I have now accomplished as completel}' and generally as possible.* * The lobes of the cephalic protuberance, even if the}- are not complete divisions, might at once be termed rings ; the anterior being denominated frontal or antennary ring ; the second, the ophthal- mic ring ; the third, the gill ring ; and the fourth, the labial ring ; to which latter the accessory parts of the mouth were affixed. The transverse protuberance at the posterior margin, which is constant!}' present, and has aheady been mentioned as the articular border, might also be termed the arti- cular ring. CHAPTER II. AFFINITY OF THE TRILOBITES TO THE EXISTING ARTICULATA. SECTION XIII. The fact that Trilobites are now generally recognized as Articulata, saves nie the necessity of speaking at greater length with regard to their affinity with the 3foIliisca ; such an investigation here being the more superfluous, since I have already sufficiently shown that the view is opposed by the general structure of Trilobites. For animals with eyes cannot be conchiferous molluscs,* certainly not, at least when they are furnished with two symmetrical compound eyes ; and this is a characteristic which also removes them from the other orders of the Mollusca, and associates them beyond a doubt with the Articulata. Among the four subdivisions of the Articulata, the Insects and Arachnoids (the heteronomous or ArachnidcB, as well as the homonomous or Mi/riojjoda) possess, however, so constant a type that it is impossible to associate the Trilobites with them ; since even the apparently similar Glomerides ai'c immediately to be distinguished from the Trilobites by the constant proportion of the numbers of their body rings, by the head not being shield-formed, by the absence of an abdomen or tail, by the aggregate of simple eyes, by the horny, articulated, numerous feet, and by many other cliaractcrs. The Trilobites, likewise, cannot be worms {Vermes), the horny covering of their body, their compound eyes, and their heteronomous type being opposed to such a conjecture. They are therefore Crustacea, and that not only on account of those negative characters hitherto enumerated, but also on account of their positive and perfectly crustacean characters. To enable the reader to understand and to appreciate the latter, I shall preface this chapter by some introductory remarks on the systematic arrangement of the Articulata, and particularly on the characters of the Crustacea. SECTION XIV. Our present system of the animal kingdom is still tinged with one fundamental error, which consists in the circumstance that we exhibit individual characters as characters of groups, instead of determining the type, which is always imaginary, with scientific precision. * When saying this, I would guard against being supposed ignorant of tlie fact, that numerous eyes have recently been observed in the species of Pecten. Previously to Krohu's interesting com- munication, I had read of this structure as probably belonging to these annuals, in the ' Diet, des Scienc. Natur.' torn, xxxviii, p. 236. 32 AFFINITY OF THE TIIILOBITES , I have endeavoured in various ways to meet this obstaele, and liave ah'eady laid down the fundamental features of my system, which I have rendered as much as possible independent of every subjective mode of consideration, in my ' Hand-book of Natural History,' (Berlin, 1837-8, 2d division.) It would lead me too far here if I were now to communicate similar results, and it would also be unnecessary, since I have already published the principal facts in the work alluded to, and am even now engaged in carrying out the subject more in detail.* I will therefore merely state that the conceptions of the homonomous, and hc.teronomom systems of the articulated fundamental type are the characteristics which, according to my view, principally determine that type : the former notion intimating an always fluctuating, indefinite numerical proportion, the latter an immutable, constant nume- rical proportion either in all, or in some of the heteronomous divisions of the body. This numerical proportion in the latter case generally exhibits itself in the multiple of a simple combination, consisting either of the number three or five, the former being generally applicable to the lower heteronomous Articulata; the latter, on the other hand, to the higher. The class of Crustacea certainly exhibits an heteronomous type throughout, having no generally equal number of body rings, but a varying one corresponding, to its character as a transition group of the Arlleulaia. The separation of the body into caput, thorax, and abdomen, of which each ought to be treated as an independent whole, according to peculiar laws, justifies the assumption of their heieronomity, which I consider as the most essential class-characteristic of the Crustacea. The two typical numbers, and as it appears generally, always the maximum number, predominate among the Crustacea in the thorax, which here, as among all other Articulata, presents the best systematic characters for the determination of the class. But the presence of these typical numbers, owing to the frequent absence of so many thoracic rings in the shape of isolated divisions, and also by the conversion of the organs of motion into accessory parts of the mouth, for the service of the head and of its organs, is frequently obscure on the first superficial observation. We must therefore, if we wish correctly to recognize the typical number of the thorax, always consider the accessory parts of the mouth as organs of motion, and these must add to the true organs of motion of the thorax, and then divide the total by 3 or 5, in order to arrive at the fundamental number and its multiple. This mode of proceeding soon leads us to the interesting result that all the higher Crustacea together with a constant type of antennae, eyes, mouth, and organs of motion, also possess an equally unchangeable numerical proportion with regard to the rings of the thorax, which is always 2 x 5 or 10, and is therefore the simple multiplication of the second higher typical number ; while, on the other hand, all the other Crustacea with fluctuating typical character of antennre, eyes, parts of the mouth, and organs of motion, never exhibit the fundamental number of 5, but either possess no fundamental number which can be considered as generally peculiar to them, or at least as far as I have been able to convince myself by exact personal investigation, and in the majority of cases possess the number 3 in a formula of multiplication which fluctuates from 1 to 4. Tiie typical coincidence of both groups, already suggested in point of several charac- teristics, renders it possible to define them with still greater certainty than this can be done * I intend to puljllsli tliis ^vork sLortly, under tLe title of 'An Attemiit at a Rational Zoology.' TO THE EXISTING ARTICULATA. 33 from the mere numerical proportion, and to establish the followin«)- g'cneral characters of them : namely, the Crustacea with the numerical proportion 2x5, have always two pair of antennae, compound eyes with facetted cornea, no simple eyes (with a few exceptions, however, as in J/ysv'y), articulated walking feet at the thorax, and always fin feet at the abdomen when this part of the body is present ; the number of articulations never less than three, or exceeding seven. They form the group of the Malacostraca of former modes of division. The Crustacea with the fundamental number of three, have fewer general charac- teristics, owing to the very circumstance that they represent a lower division, but I have always found in them compound eyes, with a simple, smooth cornea ;* sometimes also simple eyes, or (occasionally) only the latter, and then in a simple number, especially when young ; they generally have fin feet, and usually in that case no feet at the abdomen, which is fre- quently very short, but in some cases very large ; there is further a remarkable uncertainty in the formation of the antennae and organs of the mouth, the type of which, therefore, is fluctuating. All run through different stages of metamorphosis, and exhibit much greater differences in the respective periods than the members of any other division. I call them Ostracodennata. The metamorphosis with its various differences seems to be the circumstance which deserves particular attention in the subdivisions, inasmuch as it exhibits itself partially as retrogressive.t partially as progressive. The retrogressive metamorphosis is not peculiar in an equal degree to all members, since it is occasioned by external circumstances ; and with regard to retrogression, as there is in reality no such process in nature in a strict sense, it cannot be a general character of the whole group, but only an indication of some members of certain sub-groups. If therefore I avail myself of it as a mode of division, I do it only in the same manner as oviparous propagation is mentioned, as a partial characteristic of some of the cold-blooded vertebrate animals, although it does not exhibit itself in all in the same wav. The Ostracodermata, then, are divided into two groups, and each group in three tribes. The absence of a distinct head with true antennae and eyes is as characteristic for the first group, among the members of which a retrogressive metamorphosis is peculiar, just as the presence of very large, frequently monstrously developed eyes is exhibited with a progressive metamorphosis ; and in the same way also very powerfully developed antennae, especially if the eyes become smaller, is characteristic of the second group. The further differences consist in various peculiarities, the explanation of which in detail would occupy too much time ; but I have put them together in a tabular sketch, and by indicating all the higher groups of Crustacea in this table, according to their most important typical characteristics, I have enabled my readers to determine by their own observation how far the Trilobites are related to each, and with which group most intimately. (See the Table, p. 34.) * In several species, for instance, in Limulus, it appears facetted «lien in a dried state, but again becomes smooth by being softened with water. t The phenomenon of the retrogressive metamorphosis, on \\\\\ch Rathkc has recently written more specially, I Lad availed myself of as a mode of division when giving lectures at Berlin, and have published this view two yeai-s ago, in Ersch and Gruber's Encyclop., vol. xxv, section i, p. 119. 34 AFFINITY OF THE TRILOBITES 2 *- « 3 be S .H o "5 -2 ^ a *j ~ o bcS -2 'S CZ3 'II o „ a o 4"| i ■5 S Oi V CS -le ;^ S o o ^ ^ H o r^ ^ ^ r, ^ o !U o a ID z .2 o o 1. The fundamental number of rings of the thorax is ßve, and its multiple is always the simple duplication (2 x 5). The compound eyes have a facetted cornea, and there are no simple eyes. The young ones resemble the old, entirely or partially, and the metamorphosis is progressive. Organs of motion always double, and the abdomen always furnished with fins. 1 1 J. 1 a PS O Head moveable, but the eyes immoveable ; no common shell of the thorax. Of the 10 rings of the thorax 3 always bear accessory parts of the mouth ; likewise 7 walking feet. Formula, 3x7. P. m S H Body flatly pressed ; al- ways seven free rings, withrow- ing or walking feet. Abdomen small, consist- ing of from one to seven joints, with fbis bear- ing gills. Many of them are pa- rasites, and in that case have rudimentary eyes and organs of motion. The young ones only possess six walking feet, and the last pair follows af- terwards with the ring of the body. REMARK. The Isopoda that live on the land have ag- gregates of sim- ple eyes. 3 •1 1 1 Body round or flat ; the fourth rinij closely jointed to the head ; therefore only six free ring's remain. Abdo- men wanting, or furnished with one joint, and very much shortened. « EJ 1 1 Body com- pressed at the sides, with va- riously fonned feet. Abdomen always furnish- ed with seven joints, with end fins, but with- out gills, which are only seated at the thorax. The youngones perfectly re- semble the old, excepting only in size. 1 g Pa o Head immoveable, with pedunculated move- able eyes; thorax entirely, or for the greater part, covered by a simple shell. Abdomen always having seven joints. Of the 10 rings of the thorax only 2 bear accessory parts of the mouth, there- fore 8 feet, of wluch the most posterior ones, or all of them, resemble fins. Form 2x8. GiUs variable, but generally on the abdo- men. The lat- ter furnished with a large caudal fin. 3 1 ^ S5 Of the 10 rings of the thorax 5 bear accessory parts of the month, therefore only 5 walking feet, the number of which on that account is 10. Fonn, 5x5. s 1 The fin feet of the last ring but one of the abdomen are stretched to- wards the pos- terior part, and form a large end fin. Abdo- men usually not closed, but extended. - 1 pi i The fin feet of the last ring but one of the abdomen are never nsed for the formation of the terminal fin, but are en- tirely wanting. The abdomen is closed a- gainst the tho- rax. s The fundamental number of rings of the thorax is t/iree (query always ?), and the multiples of it vary from 1 to 4. The compound eyes have a simple, smooth cornea. The young of iJl the species are monoculous, and generally have only antennae and palpi as organs of motion. They undergo a metamorphosis, and are essentially iiihabitants of the water. g 1 f Ö o o They always have eyes, and generally anten- niB. The number of thoracic rings varies from 1 to 4 X 2. Tlie sexes are separate ; the meta- morphosis is progressive. They never affix themselves, and are never parasites. B. Ambula- tory feet at the thorax, giU feet at the abdo- men; the latter 3 § gilfs. N umcri- eal proportion in both divi- sions of the body 2x3. Compound and simple eyes. Articulate tho- rax and abdo- men, each co- vered by a larn;e shield-formed sheU. > 1 ^ 1 A. Notliin^ but homonomous organs of motion, onlycalculated for rowing ; true gills, aud from 1 to 3 pairs of accessory parts of the mouth. 1 gi Feet consist- ing of unarti- culated, cleft, fringed, mem- branous lobes. Compound and simple eyes; ar- ticulated tho- rax and abdo- men. Number of rings in tlie thorax 4x3; in the abdomen 2 to 6 X 3. ».WithasheL a. Shell double lobed. Limniadiidts. ß. Shell shield- formed. Apodidre. b. Without a sheU. Brunchipidce. > 1 Feet articu- lated, simple or cleft in two, with long bris- tles. Number of rings 1 to 3X3. a. Gymnota s. Copepoda. Without any material shell, •ivith articulat- ed thorax, and articulated ab- domen. Long feelers. b. Ostracoda. With a large bivalvcd shell, simple eye, and unarticulated abdomen; short antennte. 1 1 1-, '1 1 i Q bS O At a mature age they generally have no eyes. The number of thoraeie rings, wiien they can be distinctly traced, are 2x3. The abdomen is wanting, or there are no organs of motion. The metamorphosis is retrogressive. ""I i P5 1 I The mouth is formed, more or less, in the shape of abeak; two pairs of an- tenna before the mouth, and six pairs of or- gans of motion behind it, il' theyare all per- fect. Affixed or moveable para- sites, with me- tamorphosis — most of them with an abdo- o . 1:1 II It 1 t Six pairs of articulated eir- riformorgansof motion. Open- ings of rectum and genitals se- parate. No ab- domen, no an- tenuie, or eyes. Metamorpliosis complete. Al- ways fLxed when aged, and encased by a thick shell or membrane. 3* 1 Unartieulat- ed,wart-formed organs of mo- tion, with cuia or bristles. Rec- tum and geni- tals opening in one cloaca ; ab- domen rarely wanting; form- ed of several jomts, and not pierced by the Ultestme; eyes simple or none; metamorphosis none or miper- « TO THE EXISTING ARTICULATA. 35 SECTION XV. A correct estimation of the characters exhibited by the Malacostraca will prove to us at once that the Trilobites cannot, at all events, belong to this second principal division of the Crustacea, for they have neither facetted eyes (see Sect. V), nor a common thoracic shell, nor a constant number of (from five to seven) thoracic rings, which would necessarily belong to them if the thoracic shell were wanting ; at least, the number could not be exceeded.* This view, however, is likewise further confirmed by the absence of feelers with a horny shell, by the enlarged, shield-formed head, by the absence of visible articulated equal feet, and by the unequal numerical proportion of the abdomen, which is covered by one common shield. Thus we disprove the aifinity of the Trilobites with the Impoda, and especially with the genus Serolis, which was insisted upon by so man}' of my predecessors. In order to manifest the incorrectness of such afiinity to every one, I have represented Serolis paradoxa (Onisc. paradoxus, Fabr.) side by side with species of the Phyllopoda (Table II, Fig. 2), and I think that the mere inspection of these different forms must convince every unprejudiced person that the opinion of the aflänity of the Trilobites with Serolis cannot for a moment be entertained. No single genus of the Trilobites has exactly the same numerical pro- portion, nor, indeed, is there any other similarity with Serolis, excepting that which is founded in the general class characteristics, and I must therefore, most decidedly, declare myself against the arrangement of the Trilobites among the Malacostraca, being unable to perceive a single reason in favour of such view. Indeed, even the moveable lateral lobes at the thorax rings of many of the Isopoda cannot be compared with the lateral lobes of the Trilobites : first, because they are moveable ; and secondly, because they belong to the leg, properly speaking, and represent the modified hip of the latter, as I shall subsequently prove ; I will here only remark that all the Isopoda, in which the moveable lateral lobes are wanting, possess in lieu of them a fundamental joint on each leg above the hip, which represents the rudiment of a lateral lobe. It can also be shown with as little difiiculty that the Trilobites have nothing in common with Liniulus, excepting a very superficial resemblance. The absence even of a separated head and thorax in this genus would render the afiinity impossible ; the hard, powerful, horny feet, however, which have been so well preserved among the petrified Limidi of the Jura formation, and which, therefore, we cannot doubt would be seen also in their analogues of a more ancient period, are a still greater reason against it. The well-known power in the Trilobites of doubling themselves up would have been a very unnecessary gift, if they had had legs like those of the Limuli, since the latter are much too large to admit of their being concealed when folded, and the animal is much too powerful to require the protection afl'orded by that process. Nevertheless we must admit that the general form of the cephalic shield, the absence of antennae, the position of the eyes, and the existence * Some Arthrosiaca, as also the Lamodlpoda, have only six thorax rings ; some Isopoda (Praniza) only five, but no member of this group exhibits more than seven. Those exceptions, however, can rcachly be explained, and their origin traced. 36 AFFINITY OF THE TRILOBITES of a simple shell of the abdomen, present facts in favour of an analogy existing between the two groups, which ought not to be overlooked, and which place the Trilobites much nearer to this genus, than among the Maloscostraca near the Isopoda. SECTION XYI. I think I have now shown that the Trilobites can only belong to the first principal group of the Crustacea, or to the Ostracodennata ; the only question being with which of the two orders assumed in this group, it stands in the nearest relation. The reply to this question will follow of itself, when we observe that the Trilobites in an advanced stage of life possessed large eyes, and on that account must have had considerable loco- motive powers, so that beyond all question they must be Aspidostraca or Eittomostraca. This result can be distinctly proved by the following reasons : 1. All Aspidostraca have compound eyes with a smooth cornea, the Trilobites likewise. 2. They are frequently covered by large shells, which widely project over the axis of the body ; the Trilobites possess quite an analogous formation of the shell. 3. These shells consist of two membranous layers, with a thin stratum of the substance situated between them. The lower layer is much more tender than the upper, quite in the same manner as we have found it among the Trilobites. 4. The Aspidostraca possess tender, soft feet, very easily injured, and such must have been possessed by the Trilobites, to account for their absence in all the fossil remains of the latter. 5. They are exclusively inhabitants of the water, and only move by swimming ; the habits of the Trilobites must have been similar, because they have no hard organs of motion suitable for crawling. 6. The Aspidostraca, at least those covered by shells, have usually very small antennae, or none at all, while among the Malacostraca they are very large, and covered by a hard upper membrane. This explains immediately why we miss these organs in the Trilobites. 7. The different subdivisions of the Aspidostraca exhibit different numbers of body and caudal rings, and correspond partially in this respect with the numerical proportions of the Trilobites. The fundamental number of the thorax divisions is exactly the same among all PsendocephaJa and Malacostraca, and differs only relatively, according to the greater or lesser number of rings which have become combined in the head. It appears unnecessary to seek for any further reasons in proof of the affinity of the Trilobites and Aspidostraca, after having exhibited so many important points of similarity between them ; I therefore now conclude this investigation with a short consideration on the true relations of affinity which probably obtain between the two groups alluded to. TO THE EXISTING ARTICULATA. 37 SECTION XVII. At tlic commencement of this discussion, and as expressing the view whicli I shall endeavour to prove, I make the following statement : That the Trilobites do not belong to any of the still living families of Crustacea, but represent a distinct group most nearly related to the Aqndosiraca ; that their organization, however, exhibits peculiarities, which at the present day do not occur together in one family, but are dispersed in several heterogeneous groups ; thus, although we have proved in the preceding paragraph that the Trilobites correspond in many essential points of organization with the Aspidostraca, and are not related to any of the still living groups of Crustacea, yet we must not neglect to observe that various important and even typical differences take place between Aspidostraca and Trilohites. These differences consist prin- cipally in the numerical proportions of the thoracic rings, since although the latter certainly vary among the Asjndostraca, they may yet be reduced to several constant fundamental numbers (6, 9, and 1 2) ; wliilst the Trilobites only exhibit a constant number of rings for each separate genus, and the total number cannot be reduced to certain, unchange- able, fundamental numbers or numerical types. In attempting to ascertain with certainty the number of thoracic rings, we certainly meet with the obstacle that we do not know, nor ever can know, the position of the sexual openings among the Trilobites, which position alone indicates with certainty the boundary of the thorax. But even if we exclude for the present the Oleneides with their many- articulated body, and in which the capacity of doubling themselves up is wanting, (since there is the greatest probability that in them the sexual opening was not situated at the last ring before the caudal shield, but on a pre- ceding ring,) yet in the other genera we have the constant numbers 6, 8, 9, 10, 11, and 13, which cannot be reduced to a common fundamental formula. If, therefore, we do not assume that the sexual opening in these genera was also situated at a certain ring of the body before the caudal shield, — say for example's sake at the sixth (2 x 3), or ninth (3 x 3), — we find ourselves obliged to adopt the view that the Trilobites, in point of the fundamental numbers of their thoracic rings, are not constructed according to the law which we have discovered to obtain amongst all Crustacea of the present world. This is a most important result, and it perfectly confirms the opinion which I have already pronounced several times, that the ancient types of organization do not correspond with the existing ones, but that they more or less deviate from the plan of the present creation. Cuvier, indeed, has acknowledged the truth of this principle, but he did not carry it out ; it has subsequently been often touched upon, especially when speaking of extinct amphibious animals, but, so far as I am aware, it has not even yet been fully recognized by any naturalist. The consideration of this subject is, notwithstanding, the means by which we should be able to show most distinctly that the organized beings of our earth were originally created according to one uniform plan, but that the nature of this plan with regard to the different types, was at first by no means so clearly and distinctly established as it appears to us now in the present representative species. The earlier types, in fact, seem to present the various peculiarities of several gi'oups passing into one another, resulting in forms 38 AFFINITY OF THE TRILOBITES which exhibit in association, although incompletely, the peculiarities now found detached and characteristic of very distinct groups. Minute and careful observation has seemed to confirm this view, and exhibits also another important fact, namely, that in proportion to the geological age of the extinct species, the rvmning of the various typical forms into one structure is more marked, and therefore the peculiar and organic individuality and dis- tinctiveness less obvious. Such being the case, it will no longer appear strange that the Trilobites, the oldest Articulata that we are acquainted ^^ith, should not exactly correspond with any one group of living Articulata ; and, on the contrary, it would rather be a matter of surprise if such were the case, for their identity with any recent family would overturn those laws which have been developed with so much labour and care in the course of various researches on the organic beings of a previous creation. If therefore any one should assert that the identical representative had been discovered of an animal whose period of existence in a living state was unquestionably very remote, and long antecedent to the commencement of the present era, we might safely assert, wherever the discovery was said to have taken place and even without seeing the supposed representative, that it is not what is thus assumed. No doubt the assertion might be credited by many imperfectly informed persons without due investigation, but the naturalist acquainted with the unity and uniformity of the great plan of Nature, and her method of producing results by laws which are invariable, will not for a moment entertain a belief of the present existence of any species of Trilobites, however comparatively insignificant the creature may be. I would by no means assert, however, tliat Trilobites wholl}' deviate from the tvpes of all existing Crustacea, for, on the contrary, many important resemblances are found, which I have already indicated and partially explained. We are even able, by a careful and accurate estimate of these resemblances, and by comparing the details of structure exhibited in the remains handed down to us, to restore those points in the organization that are wanting by considering the affinities with recent forms. It is this task which I now proceed to perform. SECTION XVIII. In order to proceed with due caution it will be proper, however, first to explain more particularly the peculiarities of that group of Crustacea with which the Trilobites are most nearl}' related, for the purpose of being able to infer thence whether they may possibly stand in a more intimate relation of affinity to an)' one subdivision of the group, or whether they exhibit a similar relation to all. According to the tabular sketch already given, the group of Aspidostraca is divided into three tribes, bearing the names of LojjJiyropoda, PhllUopoda, and Pcccilopoda. These denominations indicate important diiferences with regard to the feet ; for the first two divisions possess soft, membranous organs of locomotion, solely calculated for swimming ; while the Fcecilopoda possess hard, articulated, walking feet, and in this group serve also as gills, and aerate the blood. This circumstance has already been taken into consideration, and an important difference between the animals of this group and the Trilobites has been thence inferred. The genus Limidtits, which con- TO THE EXISTING ARTICULATA. 39 stitutes this group, corresponds only in some peculiarities of the cephalic shield or of the cephalothorax with the Trilobites, and for this reason, and since it is only a partially analogous form, I shall not say more concerning the group. Of the two other groups, the Lopltyropoda generally exhibit a slighter or less compact form of the body, and rather large antenme ; they also have cither a single eye, (which in some species is large, in others small), or two very small eyes, and therefore exhibit characters which correspond less completely with the type of the Trilobites than the more considerable size of body, larger eyes, and undeveloped antennae of the PhyUopoda; I therefore do not hesitate to recognize in the latter the nearest affinities of the Trilobites, for which reason I shall now describe their organization more particularly. SECTION XIX. The Phi/Uopoda have a soft, fleshy body, the thorax generally consisting of eleven members, bearing the same number of fin-shaped organs of motion. The head is an independent division, to which, besides the antennae and organs of mastication, a rudi- mentary pair of feet is attached, by which the number of feet of the tliorax is increased to twelve (4 x 3). The other organs vary ; there are generally two pair of antennae before the mouth, but these are either remarkably small, as in Ajms ;* or only one pair consists of distinct antennae, whilst the other is prehensile, and assists in the act of copulation, as in BrancMpm ; or else, lastly, the former pair of antennae assists in locomotion as a fin-foot, while the latter is a short, almost jointless, lobe of flesh, as in Limnadia. The eyes present similar differences. There are two large compound eyes, and one simple eye, in all Phyllo- poda, but the former are either planted on a long peduncle, and are moveable, as in Brancliipus, or are immoveable, and in that case partly united in a circular form, as in Limnadia, and partly arranged in two distinct semicircles, as in Apms. The simple eye stands between them at the extremity of the forehead, or if they are close to each other is behind them. It is remarkable, however, that BrancMpm, the genus having laro-e, greatly projecting, moveable eyes, does not possess any protecting covering, whilst Ajom and Limnadia are so provided, the protecting envelope in the former of these genera {Apus) consisting of a head plate enlarged into a shield, which only, indeed, covers the head, but is intimately connected with the body of the animal ; while in the latter, on the other hand, {Limnadia), it consists of a shell formed as in shells with double flaps, and this shell is placed at the junction of the head and body, (and therefore, properly speaking, also at the head,) and can be opened and shut below at the will of the animal. Another important relation harmonizes with the presence of this shell, namely, the structure of the abdomen, which in the genera covered by shells, exhibits no marked distinction from the thorax ; and even (which is the only case in the whole class of Crustacea) bears feet constructed in exactly the same manner, only successively smaller, and not merely is there a single pair at each ring, but at first two at each, and afterwards even three or four. The number of organs of motion is * Apus, Branchipus, and Limnadia, are represented in Table VI, Figs. 1, 3, and 15. 40 AFFINITY OF THE TRILOBITES thus increased in an extraordinary degree, and the difference between thorax and abdomen disappears entirely on a superficial observation. It is only the internal anatomical examina- tion which determines the boundary of the two divisions, and exhibits the sexual opening behind the eleventh ring, but this is seen even in Apns, exactly at the same spot at which it is situated in Branclilpus. The two last rings are, however, excepted from this remark- able and unique instance of the approximation of the abdomen to the type of the thorax, these rings retaining the shape of the abdomen, but bearing no further organs of motion, and terminating with simple horny appendages, as in Limnadia, or with articulated ones as in Apus, and these are attached to the remarkably developed last joint of the body. Between them is the anus. Brancldpus shows no trace of any of these characters, its abdomen, consisting of nine joints, has no feet; and instead of the horny appendages, we find in them either two large soft caudal fins, or, as in Artcmia, nothing whatever to represent them ; but the females here also possess distinct egg-capsules at the commencement of the abdomen, and the males smaller seminiferous sacs. Nothing of this kind, however, is found either in Apii>i or in LiuiuacUa ; the males in the former bearing such a resemblance to the females, that the former a few years ago were not known at all,* and Mr. Kollar, of Vienna, was the first who discovered them ; f while in the latter the males possess organs of copulation in the first modified part of the thorax, (or at least this is the case in a species which has in consequence been detached to form the new genus Estheria). The females of Apns, however, can easily be recognized by the sacs, which are situated at the eleventh pair of feet, and which serve as the repository of the eggs, but are placed towards the back, beneath the shield. The feet of these animals exhibit also a difference corresponding with that presented by the structure of the body, both in the case of those which have shells and which are without such defence. Tliey consist in all cases of soft, membranous lobes, which are mei'ely supported by muscular bundles, the circumference of which is intersected at intervals irregularly, and at the margin they are covered with long, fine, hairy fin-bristles. At the inner side six principal lobes are seen, of which the first four are of nearly equal size in Limnadia (Fig. 15, B) ; but in Ajms (Figs. 9, 10, 11) the first (B) differs very much, and the succeeding ones resemble one another, only they become larger from the basis to the point. In Branchipus, however (Fig. 12), they become smaller in the other direction ; and the fifth lobe, the last but one, which is very long and small in Limnadia, is very broad and rounded in BraticJripiis, and in Ajms is similar to the preceding lobes. The last, the sixth, lobe is connected by a special joint with the rest of the foot, and is therefore more freely moveable ; it has a long stretched, rudder-like form, and seems to be the most important of all the divisions of the foot. Every foot, at the opposite outer side, bears a bladder-formed gill (K, in the plate), and is also provided with broad lobes of membranes. Of these we only find one very large lobe beneath the gill in Apus and Limnadia (L) ; but in BramUjms there are two lobes (which, however, are both situated at the gill), one of them a large one, * In a work, otherwise very excellent, h\ E. G. Zaddack, (de Apod, cancriformis anatome et evolutione, Bonn, 1841, 4to), these animals are described as hermaphrodites, which probably is only to be attributed to a defective microscopical aualj-sis of the organs of generation. t 'Isis,' 1831, p. G80; Froriep's 'Notizen,' 1833, vol. xxxviii, p. 148, etc. Mr. Kollar had tlie kindness to present me with a male specimen. TO THE EXISTING ARTICULATA. 41 similar in circumference to the latter, and placed next to it (Fig. 12, L) ; and the other smaller, and situated rather higher upwards (I). The gill is easily known by its bladder-like form, by the want of muscles extending towards or penetrating into it, and by the absence of fin-bristles at its margin ; while all the other lobes are surrounded both by fin-bristles and are also supported by muscles, which latter extend towards them, and serve to assist in locomotion. The lobes of the outer side, although the largest, are yet the most delicate and the least protected ; they are, however, furnished with muscles, and they therefore appear to be more intended for the protection of the gill, than for locomotion. This is further confirmed by their inverted position in relation to the gill in the case of those genera covered with shells, as well as in the naked genera. I would therefore call them "protecting lobes." There is no doubt that the absence or presence of a shell is the main distinctive character of the group ; and since a classification in which the natural characters are placed in opposition becomes necessary, I have planned the following formula : First Group. Genera with SJicUs. Cliaracfers. — Eyes immoveable, placed closed to one another. The rings of the body partialhr spinous ; those of the abdomen likewise bear feet ; the last is a horny capsule, furnished with various appendages. Gill of the feet attached above the protecting lobe. Division A. — Shell with two Flaps. Eyes united into a circular group ; anterior antennae having two rows of filaments, posterior simple ; — all the antennae at least as long as the head. No accessory parts of the mouth, fifteen abdominal rings, the moveable terminal spines unarticulated. Genera. — Limnadia, Estheria. Division B. — Shell, Shield-like. Eyes crescent-shaped, more distinctly separated ; the antennae scarcely recognizable ; two pair of accessory parts of the mouth behind the jaws ; first pair of feet (not including the real first, but rudimentary pair) furnished with four long, many-jointed fibres, instead of the fin-lobes ; abdomen formed of more than fifteen rings, the terminal spine of the last ring long, moveable, and articulated. Genera. — Lepidurus (with a flap between the end bristles), Apus (without this flap). Second Group. Genera without Shells. Character. — Eyes pedunculated, moveable. Antennae unequal ; the anterior consisting of simple fibres ; the posterior tongue-shaped, and serving as organs of copulation. No accessory parts of the mouth behind the jaws ; the gills of the feet beneath the protecting lobes ; abdomen without feet and smooth ; ovarian and seminiferous sacs, external. Genera. — Branchipus (abdomen furnished with nine joints, with two caudal fins), Artemia (abdomen furnished with six joints, with two terminal lobes). 6 42 AFFINITY OF THE TRILOBITES SECTION XX. The near analogy of the Trilohites to the PhyUopoda appears to me to be especially illustrated by the points of resemblance already alluded to ; viz. the double large eyes, the undeveloped antennse, and the very soft membranous feet. But Bratwhipus seems to be that form among them, with which the organization of the Trilohites has the nearest affinity. In order, however, to render this quite manifest, I have drawn the shell of a Trilobite round the body of a Branchipm, and thus obtained an imaginary form (Fig. 16, Table VI) ; which, I think, will scarcely leave a doubt respecting the near analogy of the two forms. Referring to this figure, the real head will be seen projecting from the cephalic shield, but with this difference in Branchipus that in it the projecting boss forming the head consists of only two divisions, the anterior of which, bearing the antennae and eyes, is smaller than the posterior, to which the branchial apparatus and accessory parts of the mouth are affixed. In Trilo- hites, on the other hand, the projection of the head is either simple or divided into four parts, and in the latter case the first is either the smallest, as in Oleiius, Triartlini-s, Trilobites Sternher(/n, and other allied forms ; or, as is sometimes seen, the first is the largest, the others being all smaller. This proportion indicates very large eyes and antennae, a view which seems verified in the case of the genera enumerated, since even the so-called species of Olenus have small eyes, while Asaphus, lUanus, species of Pliacops, and Oyygia, have very large ones. For the same reason we might also draw an inference from the development of the antennae, and assume that one pair of them perhaps, as in Branchipns, were organs of copulation. I consider myself further justified in this assumption by the structure of the lower side of the head ; for a very large, broad, cephalic shield, such as that seen in Asaphus (Table VI, Fig. 8, a), and Paradoxides (Table I, Fig. 7,) indicates developed organs towards its side. The anterior enlargement beside it (Table VI, Fig. 8, b, h) may perhaps have been the peduncles of linguiforni antennae, or the latter may have been attached to the lateral enlarge- ment beside the cephalic shield (Table VI, Fig. 8, c, c), while the anterior enlargement bore small, short, true antennae, as in Bra/ic/tipi/s. If this conjecture is well founded, we may also easily understand why the anterior division of the head of the Trilobites is so large, sometimes even (as, for instance, in PZ/acops — Division A, — and Asaphus) obliterating the succeeding divisions, and thereby causing an undivided projection of the head. The wide-arched space of the shield beside the projection of the head beneath the eyes, would also be very well calculated for the reception of such linguiforni antennae. The moveable upper lip was unquestional)Iy affixed to the posterior margin of this lower pi'ojection of the head (the real Ch/peiis, Table VI, Fig. 8, d), and the size of the lip depended on the width of this margin, and on the magnitude of the incision. As in Apiis and Branchipus, this lip covered the upper jaw, the form of which perhaps rather resembled the upper jaw of Apus than that of Branchipus, since the hard horny shell also indicates more solid organs of mastication. The third division of the projection of the head, which is generally the largest after the first, probably corresponds with the position of the jaws, and formed the basis of attachment for the muscles. It represents that ring of the body which, in the typical form, is independent, and has the organs of locomotion changed into gills ; and since only a TO THE EXISTING AIITICULATA. 43 smaller division exhibits itself behind this one, and anterior to the articulation of tlie succeeding one, we might thence infer that there were accessory parts of the mouth, an inference which is highly probable, since in /Ipus there are also two pair of accessory parts of the mouth at that spot. The structure of Limnadia and Branchipus, neither of which possesses any true accessory parts of this kind, exhibits, however, an indication that these may likewise have been wanting in those Trilobites characterized by a simple projecting head. Such genera are Asaphis, Nileiis, Illanus, Trinudeus, 0(/i/(/ia, and Phacops (Division A), all of which are Trilobites in which a pair of small bosses are always exhibited more or less distinctly behind the large, simple projection of the head. These little bosses seem to indicate the traces of the rings to which the jaws were attached, but I should be inclined to question the existence of accessory parts of the mouth in all S'uch Trilobites ; and this affords a decided reason for separating the species of Phacojjs referred to Division A, even generically, a view which is also favoured by the whole structure of the body. It will now probably be admitted that in the structure of the PhyUopoda may be recognized the typical characters exhibited in the general configuration and proportions of the head in Trilobites, and that those writers have been fully justified who have considered the two groups as related and nearly analogous. It will be seen as we advance, that there are still additional reasons in support of the view I have taken, especially when we come, in the next place, to consider the structure of the feet, since the varying numerical proportion of the rings which compose the body of Trilobites separates the group from PhyUopoda, where this number is constant (4 x 3 — 1). SECTION XXI. There is good proof that the feet of the Trilobites must have been soft membranous organs, for the absence of the slightest remains of these organs in the numerous specimens observed is of itself sufiicient evidence of the fact,* and it can indeed scarcely be supposed that hard horny extremities should be affixed to a soft membranous abdominal surface ; since they would not have then possessed that firm basis, which all solid organs of locomo- tion require, in order that they may be properly available. That this abdominal surface also must have been of a membranous nature seems quite clear, since it has in no instance been preserved in a fossil state, whilst the hard, horny, perhaps calcareous, dorsal surface is invariably retained, and there can be no reason why the latter only .should have been handed down, if the former was also hard. We may then safely conclude that it was soft and easily destroyed, and I would only have the reader refer to the rings in the tail of the Crustacea, formed in a manner very similar to that observed in the case of the Trilobites, in order that he may be convinced that if there had been hard and solid coverings of the * Eichwald (1. c. 39), Goklfuss, and Coimt Sternberg, as is well known, fancied they recognized feet in the remains of some Trilobites ; but the representations and descriptions they have given are too indefinite to enable us to draw any certain conclusion. Eichwald's description certainly mentions the number of joints (five) and the size of the foot (foui- lines) with greater exactitude ; but even then it is very unsatisfactory and obscure. 44 AFFINITY OF THE TRILOBITES abdomen, they must have been, as in the other Crustacea, directly attached to the hard upper shell, in order that there should be a sufficiently solid basis for the organs of locomo- tion. But we may well inquire how all such solid girdles inclosing the abdomen could, if they ever existed, have been broken off with such perfect regularity that they have not even left a single vestige. Such an assumption is beyond the bounds of probability, and yet we must suppose this to have been the case, if we suppose that the abdominal surface of Trilobites was provided with a solid covering like that of the back, and the assumption is equall}' necessary if we believe these animals to have had hard horny extremities, since such extremities are never found in the Articulata unless accompanied by a solid thorax. Considering then that all traces of the extremities are absent, we may be permitted to assume that the feet of Trilobites were too soft and delicate to have left even their impressions, and this is precisely what might have been expected, if my view of the affinity of these animals to the Phyllopoda is correct ; but although this, and other reasons already given, might of themselves be considered sufficient to establish the fact, it may be proved yet more distinctly by referring to the power possessed by most species of the extinct family to double themselves up, a faculty often exhibited in the specimens found fossil which have been preserved in this form. In performing this evolution the animals in question arched the back, and bringing the caudal shield in contact with the under part of the head, concealed all the abdominal surface beneath the hard horny coating of the upper side. Now there is no imaginable reason why the animal should have been endowed with a power of thus rolling itself into a ball, if the under side of the body were defended with a horny or solid shield ; but we can well understand the importance and meaning of it, if the under side Were, as we suppose, undefended, for it is then a simple effort of nature to protect these soft and vulnerable parts against external violence. It may, indeed, be said that some genera, such as Odontuphura, Oc/ijc/ia, Olenus, &c., were not endowed with this faculty, and that therefore no general inference can be drawn, but this, in point of fact, is not a valid objection, since it appears, from the frequent absence of all remains of the hard covering in the case of these genera, that their shells must have been softer and more tender than the shells of other Trilobites, and I think there is reason for concluding that this was the case, from certain specimens which I have obsei'ved and examined of Olcnus gibhosus from the alum slate of Andrarum. In this case, if the shell were thus thin and tender, as in Apm, the power of doubling the body together into a ball would have been useless, as it would offer no protection. Indeed, in these cases, the lateral lobes are so constructed that undefended spaces would have been left if the body had been doubled, so that no advantage would have been gained. We may therefore conclude that even in those cases where the body does not appear to have been capable of being doubled up, the feet were still soft^ and we may venture to assert that in the OlenidcB the impressions of the feet themselves would have been found, if they had been as hard as or harder than the soft covering of the body of these animals. Proceeding, however, with the comparison, let us now consider the structure of the extremities of the living PhyllojMda. They exhibit, as we have already seen, only one principal type, modified with regard to the arrangement of the gills, and this modification depends on the presence or absence of a horny or calcareous covering of the body. Among the Trilobites whose body was provided with a shell on the upper surface, and which were TO THE EXISTING ARTICl LATA. 45 even protected by lateral lobes, we should certainly expect to find that modification which is characteristic of the shell-bearing Phyllopods, but we are not at lil)erty to assume any close analogy, since different families of animals, however nearly allied, do not exhibit the same arrangements in detail, each particular organ not being similar in allied groups, but such groups rather exhibiting general relations, and often showing marked differences in particular points of structure. This law is illustrated in other ways in the case of the Trilobites, and we cannot doubt its universality ; so that in giving a certain form to the feet in the restored figure (See Plate VI, Figs 7, 8), I have done so rather intending to indicate what they may have resembled, than with any idea of assuming their actual form. I merely assert that these organs were soft, membranous, and fringed, adapted for locomotion in water, placed on the abdominal portion of the body, and extending sidewise beneath the lateral lobes of the rings, as shown in the ideal transverse section. (Fig. 7.) These feet were also indented, and thus divided into several lobes at the open lower side, and each separate lobe was furnished at the margin with small bristles serving as fins. The last and external lobe (c) was probably longer, smaller, and more moveable, and reached to the termination of the protecting shell- lobe (a), bearing a bladder-shaped gill {I/) on the inner side. The protecting lobes of the feet of the P//////oj)oda were probably entirely absent in the case of the Trilobites, the hard shell aff'ording sufficient protection, and the space beneath its lateral lobes not being large. How far along the body the feet extended is a matter that 1 must leave undetermined, but I am inclined to suppose that they may have reached the abdomen, as in Jpus, since the caudal shield frequently exhibits the same impressions as the lateral lobes of the thorax, and these impressions were no doubt connected with the existence of feet. The oblique transverse furrow at each of the lateral lobes indicates perhaps that the foot was situated, or perhaps partly attached behind it, at the broader part, which issues from the ring of the axis, whilst the smaller anterior part of each lobe was adapted for articulation with the preceding one, at least in those genera possessing the capacity of doubling themselves into a ball, where there seems to be a deeper insertion at the spot where the lateral lobe turns itself downwards, in proportion as the facility the animal had of doubling itself up is greater. Since also the anterior oblique surface of the lateral lobes, which was pushed beneath during the operation of doubling up, never reaches further than to this apparent point of articulation, this circumstance renders still more probable the supposition of a more intimate connexion of the lateral lobes with one another, from the axis up to this very spot. It may also perhaps be a subject of investigation, whether the feet of Trilobites resembled each other in shape and size, as in Branchipm, or whether the anterior were different from the rest, and the posterior ones became gradually smaller, as in Jpm. Such questions are no doubt difficult to answer, but still there are certain circumstances which may help us in coming to a probable conclusion on the subject. And first of all I do not iinagine that any of those Trilobites capable of rolling them- selves into a ball possessed the peculiar swimming apparatus observable in the first pair of feet in Ajnis ; since this apparatus, consisting of long appendages projecting far beyond the margin of the integuments, would seem to require special organs of retraction to admit of being folded and concealed quickly and safely while the animal was rolling itself up at tlie moment of danger, and this difficulty would exist even if they were not so 46 AFFINITY OF THE TRILOBITES long as in Apus. I presume, therefore, that in this respect the Trilohites resembled Branchipus rather than Apus ; or that those at least which possessed the power of doubling themselves up had the anterior pair of extremities perfectly similar to the rest. And this, indeed, appears also to have been the case, from the equality of the thoracic rings observable in Branch'qms and in many Trilobites capable of doubling themselves up, this equality appearing to correspond with a similar equality in the dimensions of the extremities attached to them. Since also in Branchiptus there are no feet attached to the abdominal rings, in this respect also we might expect a correspondence with the group of Trilobites now under consideration, and this seems the more probable in the case of those genera amongst them which have a short axis, and no lateral ribs on the caudal shield {Asaphm, Illamtn, NiJeus, Aiiqyyx). For similar reasons, however, I assume that this structure obtained also in the other genera {Calymene, Homahnotus, Phacops) capable of doubling themselves up, and also in others {Oc/ngidce, Odonfoplcuruhe) not having this power, but characterized by equal thoracic rings. In these, however, the existence of abdominal feet may perhaps be inferred from the lateral furrows of the caudal shield. On the other hand, it appears pi-obable, from the decrease of size observable in com- paring the anterior with the posterior portion of the body, that in the other groups (the OlenidcB and Campylopleiira), in which the animal was not able to roll itself into a ball, the extre- mities were not all of equal size, but diminished towards the posterior part of the body, with the diminution in the size of the rings ; while the thoracic rings passed gradually into abdominal rings. This is the case in Apus and Limuadia, where the rings increase a little at first, but then diminish in size from the centre of the thorax, and, becoming progressively smaller, pass into the rings of the abdomen. From the analogy here presented, we might also expect that the first pair of feet from the thoracic feet of the Oleuidce and Campylopleura were pro- vided with filaments instead of fins, or that at least the antennse of the head were larger and more like those of Limnadia, while in other Trilobites they must certainl}^ have been short and small ; and they could not have projected beyond the margin of the cephalic shield, for the same reason which prevented the development of the lobes of the first pair of feet into filaments. SECTION XXII. Convinced that the reasons already offered will be deemed sufhciently conclusive to satisfy the unprejudiced reader, I venture now to offer the following deductions and general conclusions : The Trilobites zoere a pecidiar fcunili/ of Crustacea, nearly allied to the existing Phyllopoda, approaching this latter family most nearly in its genus Branchipus, and forming a link connecting the Phyllopoda with the P^ecilopoda. In order, however, to estimate fairly the affinity of the Trilobites with the Phyllopoda, we must not lose sight of the important fact, that the Trilobites differ not only from the Phyllojjoda, but from all other existing families of Crustacea in the varying numerical pro- portion of their thoracic rings ; a peculiarity neither exhibited at present as a characteristic of any natural family among the Crustacea, nor in any of the heterogeneous Articulata. TO THE EXISTING ARTICULATA. 47 This peculiarity occurs, it is true, among the Aspidosfracn (a group of the second great division of the Crustaceans), but only in a modified form, the difference in the numerical proportion being always reducible to one fundamental number. This law is apparently not observed in the case of the Trilobites. It would seem then that the relation existing between the Trilobites and the existing Crustacea is one rather of analogy than affinity, so that the whole group may be considered as a separate division, corresponding with the Jspidosfraca in the formal variation presented from the typical character, but not to be looked on as a nearly allied or similar group to this or to other tribes. Putting out of the question the important difference exhibited in the numerical pro- portion of the thoracic rings just alluded to, this analogy to the Aspidostraca might certainly have been considered as very close — all the other relations of organization, so far as they can be traced, corresponding very accurately — if it were not for the structure of the extremities. These, indeed, which are hard, horny, and articulated in a subdivision of the present Aspidostraca, were probably entirely absent in this form in Trilobites ; but in other respects all the typical characters of the two groups will be found to correspond. The present, however, appears to be the proper place to institute a still further investi- gation into this subject, which may serve as an additional illustration. SECTION XXIII. It follows as a matter of necessity that the Trilobites, belonging as they did to the great natural division of articulated animals, must have been subjected to a periodical growth, during which their horny or stony cases were thrown off and exchanged for new ones. This has been already alluded to by Wahlenberg, who has also suggested that some supposed new species may have been founded upon these cast shells. I am not, indeed, inclined to agree to the probability of this assumption ; but in order to illustrate my own views on the subject, it will be necessary first to describe the process of exuviation and develop- ment of the recent Pliyllojmdn. SECTION XXIV. All Pliyllopoda are subjected to a true metamorphosis, and that a progressive one. They leave the egg as unarticulated pyriform animals, and at the anterior thicker extremity of this pyriform body we perceive one simple eye, two pairs of unequal oar-shaped feet, rudimentary antennae, and an organ of locomotion, in addition to the two pairs of feet which subsequently converted itself into the real branchial apparatus.* The young animals are always quite naked and destitute of shells, whether the parents possess shells or not. If the * Fig. 14, in Table VI, represents the young of a Branchipus immediately after its emergence from the egg; Fig. 13, the young of Apus after the first moult — a indicates the small antenna;, b the large ones, c the foot of the branchial apparatus, d the rudiments of the subsequent feet. 48 AFFINITY OF THE TRILOBITES latter be the case, the young never receive a protecting covering ; if, however, the parents have shells, then the first traces of it are seen immediately after the first moult, in the form of a membranous fold, which issues from the neck, and which at once covers one half of the body. The young animal, after this period, has become considerably larger, and its body has become thicker and exhibits lateral notches behind the third organ of locomotion, from wliich the feet gradually develop themselves. The little animal still retains its first three organs of locomotion in an unchanged form as long as the feet remain imperfect ; as soon, however, as the feet (which grow laterally from the body) have attained their relative development, in proportion to the dimensions of the animal, the former organs of locomotion begin to diminish, and are gradually metamorphosed into the form exhibited in the full grown animal, which is frequently very rudimentary. It can then be distinctly seen that they are the true tentacula of the developed animal, and that according to their size in the subsequent stages of existence .they are more or less diminished or modified. The formation of the eye progresses equally with this metamorphosis. At first it is a simple small point or dot, and first appears about the time when the anterior half of the thoracic feet have formed them- selves into isolated organs ; but, besides this little dot, there are a couple of other dark spots in the head, which simultaneously and gradually with the other organs form themselves into compound eyes. A very short period of time is required for the formal development of the rest of the animal, for the subsequent structures are already conveniently isolated and per- fectly formed when the young animal has scarcely reached the hundredth part of the dimensions it is afterwards to attain. From this time forward, therefore, it advances regularly in its growth, and casts its membranes from time to time, at longer or shorter intervals, as the rapidity of its growth may demand. The cast-off membranes are split along the whole length of the back, and the animal draws forth all parts from this opening gradually in such a manner that even the smallest hair remains affixed to the old membrane and forms itself anew on the new membrane. The cast-off membrane, however, consists only of the epithelium, never of the real cutis, and it is therefore ver}^ thin and delicate. The Trilobite remains which are said to have been produced from such exuviae are thus probably mere impressions, and do not exhibit remains of the shell itself, since distinct evidence of its having been cast off would have been preserved in a longitudinal section along the centre of the back, and such a section not having been yet observed in any Trilobite, I consider the opinion expressed by Wahlenberg, that in many supposed Trilobite shells we have only the cast-off membranes before us, to be incorrect. It may still be thought probable, however, from the nature of the metamorphosis of the Phyllojmda, that Trilobites experienced a similar change, nor do I at all question the possibility of such a view being correct. On the contrary, I am inclined to recognize the vestiges of such early stages of the animal's growth in the obscure shields which have been supposed the types of new genera, under the names Agnodus and Batfus ; for, on carefully examining specimens of the former, we find not only a singular variation in size, occurring as they do from the dimensions of a mustard seed to that of a pea, but also a perceptible difference in the form of their constituent parts, and I think I can distinguish four different forms, which may be brought under two groups. Before, however, explaining these, I shall describe the Ai/nostus shield in general, referring for illustration to the representations. TO THE EXISTING ARTICULATA. 49 SECTION XXV. On the othei- liand, however, there arises a very natural suggestion, that the Trilobites may have undergone a metamorphosis similar to that described as characterizing the Phi/Uopoda. I by no means question the great probability of such a modification, but there is as yet no distinct evidence in support of it, for up to the present time no one has been fortunate enough to discover a specimen in the young state, offering any distinct indication of gradual development or metamorphosis. My original notion, that the so called genus, Battiis, was founded on the shields of the heads of young Trilobites, has since been dis- proved by Dr. Beyrich, who has shown, on the other hand, the probability that these shields belong to a particular genus of Trilobites, the one form of them covering the head, and the other the tail, while the two were connected by an articulated body formed of two rings. This genus we shall afterwards describe more in detail in its proper place. SECTION XXYI. Although, according to these observations, the develojiment of the Trilobites has not yet been proved identical with that of the P/i^Ilojjodu, there can still be hardly a doubt that there exists a completely analogous organization in the two groups, and a circumstance which has hitherto been overlooked seems to render this analogy still more probable. The three principal stages of modification of the fundamental type, which at present exist in the three families of the Plii/Uopoda above described, likewise seem to be presented in the case of the Trilobites. In the former group we observed that there are — (1) Naked Phyllopoda {Bra/ichijjus) ; (2) Plii/Ilojjoda with a simple horizontal shield {Apus) -, and (3) PhyUopjodu with a bivalve, perpendicular shield {Limuadia). Precisely the same differences of structure are also found among the Crustacea that lived at the period of the Trilobites, and thus the analogy of those early types with their present representatives, the Phyllopoda, is confirmed in a very singular manner. Besides the true Trilobites, of which the broad, flat, perpendicular shield leaves no doubt that we must recognize it the analogue of the simple perpendicular shelled Apu>i, we find also in the Palaeozoic strata the remains of two other crustaceous animals, one of which {Cytheruut) was covered with a bivalve shell, offering a perfect resemblance to that of Estheria, while the other {Eurypterun) was entirely without any shelly covering, and seems to have been analogous to Branchipus. Of Cytherina nothing has been preserved but the shell, and, according to Hisinger's figure,* it so perfectly corresponds in structure with Estheria,^ that it is scarcely necessary to say another word respecting the relations of afiinity of the * Lethsea Suecica. t See Strauss, in 'Museum Senkeubergianum,' torn, ii, p. 110, Table ^ II, aud the still better figure given by Joly, in the ' Aunales des Sciences Natur.' Nouv. Sor. torn, xvii, p. äü3, PI. 7-9. 1842. 7 50 AFFINITY OF THE TRILOBITES two forms. It must l)e evident to every naturalist, that to recognize the analogues of the genera Ci/pris or Ci/lhere in these shells, is far less probable than the affinity now suggested. The more recent forms obtained from the fresh-water limestones of the Weald, and described as Cyprisfnha, may, however, have really belonged to this genus. To prove by a priori reasoning that Euri/pterus was a shell-less Trilobite, just as IhancUpus is a shell-less Phyllopod, may appear difficult ; yet even in this view I think I am fully justified. The figures which Harlan has recently given us in his ' Medical and Physical Researches,' p. 298, leave no doubt in my mind on the subject ; and it is from the study of these figures, and from the similar one given by G. Fischer (Notice sur I'Eurypterus de Podolie, Moscow, 1 839), that I have derived my conclusions. The animal, according to the description, possessed a head which appears broader than the glabella of the Trilobites, because it was softer and compressed, but otherwise corresponds with it in form. We recognize in it two large lunate eyes, in which the black pigment of the centre may be very well distinguished from the glassy spheres and lenses extended above it, as the figures of Harlan distinctly show. These eyes were also unquestionably compound, and had a simple, smooth, horny membrane. Three pair of organs seem to be affixed to the lower surface of this head ; two of them being somewhat small, and situated at the anterior margin, and the articulation of which is no longer recognizable, although the long bristles with which they were furnished appear quite distinct. 1 take these for the antenujE, and suppose them to correspond with the first two organs of locomotion of the Phi/Uojioda. The third pair of organs of locomotion of the head were longer than the two others, thicker, more distinctly articulated, free from bristles, but furnished at the end with hooks ; they probably formed the accessory pair attached to and forming part of the mouth, and were useful to the animal when seizing its prey. It decidedly appears, from Figure 2 of Harlan's Plate, that there followed behind these three pair, and at the first thoracic ring, a couple of large, broad, articulated, but soft fin-feet, the number of joints of which appears to have been five. These also undoubtedly bore bristles at their margin, but their delicate nature prevented the impression from being retained. Together with this first thoracic ring, I recognize in Harlan's figure (Fig. 1) twelve rings, although in Fig. 2 there are only ten distinctly to be seen, but in this case the extremity of the abdomen is injured ; Fischer has represented fourteen rings, and a still further number is indicated in his figure. This impression, indeed, seems generally to point to specific differences, on account of the sharp lateral prongs of the rings of the body ; but we might also take these lateral lobes for the extreme ends of the fin-feet, and assume at the same time that they were much smaller than the first pair, according to the analogy of Jjms (Table VI, Fig. 1). I am myself decidedly of this opinion, and consider that it is not feet that are visible in the figures of Harlan and of Dekay, the animal having been too much compressed by the petrified mass during its inclosure, to admit the possibility of the extreme ends of the feet projecting in this manner. The softer abdominal side of the body, together with the feet, may, however, have been already cast off in these very specimens, and this is another and also a very probable conjecture. I believe in other respects that of the whole number of the rings we must reckon nine as belonging to the real thorax, the remainder being abdominal. The great diminution of the body from the ninth ring, and the equal breadth of the succeeding rings arc reasons in favour of this conjecture, and the deviating formation of these first rings in TO THE EXISTING ARTICULATA. 51 Fischer's figure may be considered as another. The first six rings certainly here appear to be much more peculiar than the three next succeeding ones ; but, considering the other points of identity in structure between this species and the North American one, we are probably justified in assuming that they must have had an equal numerical proportion, so far as the thorax is concerned. According to this view three, or perhaps six rings would come to the abdomen, and this proportion would correspond with the prevalent type both of the Trilobites and Phyllojioda. A separation of both divisions of the body in six and six, or in six and nine rings, is, however, also conceivable, and indeed easily to be accounted for by the analogy oi Apus and also of the species oi Pkacops referred to the second division. SECTION XXVII. Having adduced so many analogies and homologies of structure between the Trilobites and the Pliyllopoih, we may be permitted to assume some similarity also in the habits of the two groups, and I now propose to add some remarks on this subject. The PhyUopoda live in stagnant fresh waters, especially in ditches, pools, or puddles, which are very rapidly produced after rain in the early part of the year, and last only till the middle of the summer, when they become dried up. During this period the animals of the tribe we are describing are usually seen in numerous companies swimming about in the water at various depths, the species of BrancJiipus being most frequently close beneath the surface of the water. In swimming they turn their back downwards, their abdomen being upwards, so that the feet touch the surface of the water, and accordingly Branckipus, has its eyes in the position in which I have represented it in Table VI, Fig. 3, and not proceeding from the head rectangularly. This position of the eyes enables the animal to look both upwards and downwards. Apus, on the other hand, which has immoveable eyes, can only look downwards while swimming on its back, and it must turn itself if it wishes to look upwards. But this is quite natural, since in each case the animal, when in its usual position, and close beneath the surface of the water, can only have its enemies below, and therefore only needs to be secured against surprise in that dii-ection. These creatures are, however, not much exposed to attack. Their prey, which consists of other little animals living in the water, they obtain during their constant swimming motion, and it is brought to the mouth by the motion of the water. Owing to this, the region and cavity of the mouth in many of these animals, when preserved in spirit of wine, are frequently entirely covered or filled up with extraneous substances. The PhyUopoda are never at rest, partially because they are entirely deficient in organs by which they could keep firm hold of anything, partially also because their motion of swimming produces at the same time the motion of the respiratory organs, which being independent of the will of the animal does not cease. I have not yet had an opportunity of observing Limnadia and Estheria in a living state, but both genera undoubtedly exist in the same manner ; I am not, however, aware whether they swim on their back. Considering the afiinities of the Trilobites with the PhyUopoda, I cannot doubt for a moment that their habits during life and their mode of existence were similar, and I therefore conclude — 52 AFFINITY OF THE TRILOBITES, ETC. 1. That these animals moved only by swimming, that they remained close beneath the surface of the water, and that they certainly did not creep about at the bottom, as Mr. Klöden supposed.* 2. That they swam in an inverted position, the belly upwards, the back downwards, and that they made use of their power of rolling themselves into a ball as a defence against attacks from above. 3. That they lived on smaller water-animals, and in the absence of such, on the spawn of allied species. 4. That they most probably did not inhabit the open sea, but the vicinities of coasts, in shallow water, and that they here lived gregariously in vast numbers, chiefly of one species. .5. That the number of species could never have been very great. This is indeed proved by the mode of their appearance in the fossil state, inasmuch as scarcely more than six or eight species have been found together anywhere in one stratum. 6. Although the number of species has not been large, the number of individuals was very great indeed ; a fact likewise observed in the living P/ii/Uopoda, of which we as yet scarcely know a dozen species, although these are grouped into about six different genera. « 7. The great differences existing in the dimensions of the present P^y/Zo/JOf/'? according to their age, justify us in expecting such differences also among the Trilobites ; and very large individuals of the latter, therefore, do not indicate a separate species, unless other differences are presented. * See 'Verst. d. Mark Brandenburg,' vou H. Klüdeii, p. 104. CHAPTER III. SYSTEMATIC ARRANGEMENT OP THE SPECIES. The arrangement of Trilobites, and their position amongst the Crustacea, now no longer offers any difficulties, and they may be most conveniently described in the following manner. If, as the observations already offered would seem to demand, we arrange the genera Cytkerina and Euri/jjfcrus with the Trilobites in a single division, we have a group parallel to the existing PhijUopoda ; to designate which we may employ Dalman's name Palceudce* and which may thus be described. The Pal^ad^ are crustaceous Articulata, belonging to the second order of the class Crustacea (divided into Ostracodermata, Aspidoatraca, and Entomostraca), characterized by the possession of two large compound eyes, by the absence of simple secondary eyes, and by having short undeveloped feelers, and soft leaf-formed feet, bearing gills. By these characters they are immediately related to the Phj/IIopoda, and might perhaps even be united with the latter in one tribe. Their principal difference would then consist in the absence of the constant numerical proportion of eleven rings of the thorax, common to ail the FhijUopoda, which must be expressed by the formula of 4 x 3 — 1. Instead of this, the Palceadce exhibit fluctuating numerical proportions in the parts of the thorax, respecting the reduction of which to a constant formula, nothing certain can be said ; because we neither know the number of the accessory parts of the mouth, nor the position of the sexual openings. These animals underwent a progressive metamorphosis, they moved by swim- ming, probably with their backs downwards, and they inhabited the ocean, living chiefly in shallow water. The whole group is divided into three families, which are characterized according to the nature of the shelly covering. First Family— EURYPTERID.E. In these there is no shell. The head, whose position is very distinct, bears two pair of setaceous feelers, and one pair of accessory parts of the mouth. There are probably nine (?) rings in the thorax, the first of which bears a pair of very large rudder-shaped feet, * See the article written by me on the Entomostraca, in Ersch and Gruber's Encyclopiedia, sect, i, vol. xsxv, p. 134. I here first explained the relations of the PalmadtE with the existing Phyllopoda. 54 SYSTEMATIC ARRANGEMENT furnished with five joints; and the succeeding rings seem to have borne similar leaf-Uke feet of an equal size. The abdomen consisted of three or six rings, and was terminated by a pair of rudder-fins (?). There is only one genus belonging to this family, and of this there seem to be three species. EuRYPTERUS, D^kay. 1. E. remipes : Somewhat slender, the terminal joint of the large fin-feet equal in length to the preceding. Length of body SYs", breadth at the upper part 1)4". Reference. — D^kay, Annals of the Lyceum of Nat. Hist, of New York, i, 12, 291, Plate XIV; and 375, Plate XXIX (1826). Froriep's Notiz. 1827, xviii, 1-3. Holl, Petref 155. Bronn, Lethaa, i, 109, Table IX, Fig. 1. Harlan, Med. and Phi/s. Research. 297. c.fff. Mitchell, Jm. Month. Magaz. iii, 291. Locality. — Slate rocks of Westmoreland, Oneida, and New York. 2. E. lacustris : Broader than the former species, and the terminal joints of the large rudder-feet much smaller. Length of body almost 5", breadth 2^". Bef. — Harlan, as above, 298. c.fy. Loc. — The grauwacke rocks at Williamsville, seven miles from Buffalo, U. S. 3. E. tetragonopfithahnus .■ Eyes placed at a greater distance from one another, quadrangular (?), the whole of the structure very slender, especially that of the abdomen, the joints probably acutely angled. Length nearly two inches, breadth %. Ref.—G. Fischer, Bullet, de la Soc. Imp. d'Hist. Natur, de Moscou, 1839, ii, 127, Plate VII, Fig. 1 ; and his Notice sur I'Eurypt. de Podolie, etc., Moscow, 1839, 4. Loc. — The transition limestone or grauwacke sandstone of Podolia, at the village of Zvilevy, twenty wersts to the south of Kamenetz. It is probable that the fossil described by Scouler under the name of Eidotea, may belong to a species of this genus. Fragments of it only are known, and these correspond with the head and the commencement of the thorax of Eurypterus, but certainly belong to a different species. See the following works respecting it: Cheek's Edinb. Journ. of Nat. Science, 1831, June, N. S. iii, 352, Plate VII. Leonhard and Bronn's Jahrbuch, 1832, 251. Bronn, Lethcea, i, 109, 98, Table IX, Fig. 2; and Hibbert, Transact. Roy. Soc. of Edinb. 1834. This latter reference I have not had the opportunity of verifying. OP THE SPECIES. 55 Second Family— CYTHERINID.E. These animals were contained in bivalve, bean-shaped shells, which are the only parts preserved. They are more or less pointed towards the external wider margin ; at the straight or dorsal margin they are rather thickened. They vary in size from K" to ^", or even (though rarely) to 1". The only genus, C}jth.enna, which belongs to this family requires as yet a more accurate study, as there seem to be several species which have hitherto been confounded with one another. The specimens from the mountain limestone are probably, however, the only true representatives of the geaus, and the species referred to Cyjiru, and found in the wealden, cretaceous, and tertiary formations, probably belong to a different and peculiar group. For the present we may consider as belonging to it — 1. C. haltica ; HisiNGER, Leth. siiecica, 10, Table I, Fig. 2, and Table XXX, Fig. 1. 2. C. pkaseolus ; Hisinger, ibid. Table I, Fig. 1, and the Antechdng i P/ii/s. och. Geot/n. of the same author, V, Table 8, Fig. 3. Klöden's Verst. d. Mark Brandenhury , 102, Table I, Fig. 10-11. Third Family— TRILOBIT^. The body covered by an affixed shell, which consists of as many rings as there are joints of the thorax (?); the head and the abdomen each similarly included in a large united shield, which, like the rings of the shell of the body, possesses a broad border that freely projects at the sides. The large eyes are situated in the lateral portions of the cephalic shield, remote from the true head. A peculiar suture passes through the cephalic shield, and divides it into two, three, or four special parts. The numerous members of this family, which have been already particularly described in the first chapter, admit of a further division into natural genera, the most suitable classification of which may perhaps be the following : 1. Trilohites incopahle of rolUng themselves ujj. The Trilobites of this division appear to be decidedly of more ancient geological date than those of the following divisions, and are principally found in the lowest Silurian rocks, but are there accompanied by some species of the other group. They are easily recognized by the structure of the lateral lobes of the body, which is such that throughout its length each preserves the same breadth, and never diminishes on the upper and external side towards the margin, a peculiarity observable in the members of the second group. The lateral lobes of these Trilobites, therefore, represent narrow parallel courses, which are usually divided in a diagonal direction by a transverse fuiTow. On a more accurate examination, however, we find that two different types predominate in their configuration, which present new differences, the details of which we need not dwell upon in this general description. The species of this first principal group are further distinguished by the smallness of their eyes, which are depressed, and have a more elongated form than the eyes of other Trilobites. Only the inner surface of the shell is known, the upper surface being absent in almost all the specimens hitherto found, ex- cepting those belonging to the genera OdontopJeura, Brontes, and Harpes. This is especially the case in those found in grauwacke, clayslate, and alum-slate. As already mentioned, this group is divided into two sections, according to the characters of the lateral lobes. 56 SYSTEMATIC ARRANGEMENT GROUP THE FIRST. The lateral lobes of the rings of the body are situated in the same plane, and do not curve or bend downwards, but terminate towards the posterior part in a more or less prominent point, some- times very long, tchich forms a somewhat obtuse angle in its principal direction with the direction of the lobe. Of this group there are further subdivisions, which may readily be distinguished from one another, being founded on the presence or absence of a large caudal shield. Division A. Trilobites with a simple, large, caudal shield {not much smaller than the cephalic shield), the axis of which is many-jointed, and equals, or even exceeds, the length of the body. Ogygiid^. To this group belong two genera, Trinucleus (with six rings) and Ogygia (with eight rings). Genus 1. — Trinucleus, Murchison (Cryptolithus, Green). Cephalic shield almost semicircular, with a margin which is dilated all round and punctated, and with posterior angles terminating in long spines ; the central glabella very convex, much contracted at its posterior part before the margin ; without lateral lobes or furrows. The eyes and the facial suture I have not yet myself been able to examine.* The body is short, the six rings narrow, scarcely half as broad as the lateral lobes, the latter with a distinct diagonal furrow, and with a fine short angle. Caudal shield triangular ; the axis articulated in six or more jointed, the sides without radial furrows ; the margin reflexed and acutely angular. Loccdity. — In the lower and middle Silurian strata. Remark. — Several species are known, from the lower Silurian strata of England, North America, Sweden, and Bohemia. Some authors enumerate only five body-riugs, probably by mistake, or in consequence of the defective preservation of the individual. 1. T. Caractaci : Limbo scuti cephalici orbicular!, conceutrice punctato ; angulis posticis subrectis, longe spinosis; caudse basi annulata, apice scuti acuto. Long. %-\]ii". Plate I, Fig. 1. • Ref—T. Caractaci, MuRCHisoN, Sil. Syst. pt. ii, p. 659, Plate XXIII, Fig. I, a, b, c, d, e. Brongn. Crust, foss. Plate IV, Figs. 6, 7, A, B, C, p. 145. Lhwyd, Phil. Trans. vol. XX, p. 243, Plate, Fig. 8. Bigsby, Jn/ials of the Lye. of Nat. Hist, of New York, i, 214, Plate XV, Fig. 1. Emmr. Diss. 51. 6. Milne Edw. Crust, iii, 331. 1. Portlock, Report, 262, Plate I, B, Fig. 3-7. Cephalic shield nearly semicircular, broader than long, the enlarged margin covered with five to six concentrical rows of little pits, from which rise small wart-like prominences ; posterior angles oblique and oj)pressed, each terminating in a long pointed spire as long as * Dr. Loven (Ofvers of Kongl. Vetensk. Ak. Förh. 1845, No. 4) describes the facial suture as running close to the margin of the cephahc shield, turning inwards at the posterior angles, and inter- secting'' the posterior margin of the shield at about the middle. In accordance with this statement, such an arrangement has been indicated in the figure of Trinucleus Caractaci. OF THE SPECIES. 017 the body ; glabella almost twice as long as broad, anteriorly rather hemispherical, posteriorly contracted, with the vestige of a knob at each side. Six distinct rings of the body, the axis of each scarcely half as broad as the lobes. Caudal shield triangular, with a slightly elevated angle at the exterior margin ; its axis only articulated to a little beyond the centre with six rings, afterwards simple : the lateral lobes furnished with six radiating striae divided towards the margin. Remark. — Described from specimcus ia the IMuseum at Halle, occurring in a yellowisli grau- wacke. Found also in the lower Silurian strata of England, North America (Montreal), and Bohemia. (Sternberg, Verhandl. d. vat. Mus. 1833, Fig. 2, b.) 2. T. yranulatus : Limbo scuti cephalici orbicul.u'i, puuctato ; angulis posticis lobatoproductis, brc\ e mucronatis ; scuto caudse subsemich'culato, rhachi tota annulata, annulis sex. Long. %". • Jief. — Ei/t. yranulatus, Wahl. «. acf. Ups. VIII, 30. 5, Table II, Fig. 4. Asaph, gran. Dalm. Pal. 43. 4, Table II, Fig. 6. Brogn. Cr. f. 36, PI. Ill, Fig. 7. Milne Edw. Cr. Ill, 332. Boeck. Gaea norm. 41. Trinudeus Lloydii, MuRCH. ^7. Syst. Pt. II, GGO, PI. XXIII, Fig. 4. Emmr. Biss. .53. 9. Milne Edw. /. c. 4. Loven, Ofcers K. V. A. Forhandl. 1845 ; 109, Tab. II, Fig. 2. Cephalic shield, like that of the preceding species, but the posterior angles produced into broad, parallel, punctated lobes, which project backwards beyond the rings of the body, and finally terminate in a delicate spine rather shorter than the lobe. Rings of the body not so narrow as in former species, and more than half as broad as the lateral lobes. Caudal shield, a segment of a circle smaller than a semicircle ; the axis indistinctly articulated ; the sides without ribs. Occurs in a black limestone belonging to the upper members of the lower Silurian series in Great Britain and Scandinavia. 3. T. fimbriatus : Limbo scuti cephalici dilatato, radiatim granulate ; angulis posticis irregulariter granulatis, subrectis, mucronatis; cauda tota annulata, annulis 12-13, long. 1". Ä/.— MuRCH. /. c. PI. XXIII, Fig. 2. Luid. Ic////oj/r. p. 97, Tab. XXIII. Emmr. Diss. 52. 7. Milne Edw. /. r. 2. Portlock, Bcporf, ^-c. ,- 264, PI. I, B, Figs. 11, 12. Sars, Isis, 1835; Tab. VIII, Fig. 4, d (certainly not the caudal shield of an Ai//pt/,r). Cephalic shield shorter and broader than in the preceding species ; the mai'gin furnished anteriorly and at the sides with radiating pores ; the posterior angles not contracted, irregularly granulated with pores, with a long, nearly straight, terminal spine. The glabella but little diminished posteriorly, with slight traces of lateral impressions, but little longer than broad. Rings of the body indistinct ; body shield oblong-triangular ; the whole axis articulated as far as the extremity, long, consisting of thirteen or more rings ; the sides with twelve radiating ribs ; the margin acutely angled. Remarks. — 1. T. nudiis^ CSlurch. I. c. Fig. 5) I am inclined to consider the same species, with the margin broken off at the cephalic shield. See Emmerich, Fig. 5.* * Note, by the Editors. Trinudeus nudus is really a species of Amjryx, as may be seen by con- sulting the original specimens in the Museum of the Geological Society of London, and stiU more perfect ones in the collections of the Geological Survey of Great Britain. 58 SYSTEMATIC ARRANGEMENT 2. Asaphus seticornis (Hisinger, Leth. Suec, second supplement, Tab. XXXVII, Fig. 2) cannot be identified with T. fimbriatus, as figured by Portlock (/. c. 263, PI. I, B, Fig. 8), and Loven( /. c. 107, Tab. II, Fig. 1) ; but is a different and liighly characteristic species allied by its rounded caudal shield more nearly to T. gramdatus than T. fimbriatus. A. cyllarus (Hisinger, /. c. Fig. 3) is, according to Loveu, the same species, the spine of its cephalic shield being broken off. 4. T. ornatiis : Limbo seuti cephalici antice angusto, estus posticeque lato, sed constricto ; anguhs posticis acimiinatis, longe spinosis. Tril. oniatus, Sternb. Ver/t. 1833. 53. Fig. 2, a. Trin. radiatus, Murch. /. c. Fig. 3. Emmr. Diss. 52. 8. Milne Edw. /. c. 3, and 332. Boeck, Gaca Norw. 42. Cephalic shield as short and broad as in the preceding species, but the border at the anterFor margin smaller, and the tubercles not radiated, but in (four to five) concentric rows ; the sides very much enlarged, with five to six rows of pores, but very much contracted again towards the posterior angle, so that this region of the margin assumes the form of the letter S. The terminal spine is long, slender, and pointed. The glabella is oval, higher, more obtuse at the anterior part, and more globose. We are not yet accurately acquainted with the rings of the body and tail. Remurk. — The statement in Murchison's work, that the enlarged margin in this species has only two rows of tubercles, I must consider incorrect ; Count Sternberg describes from four to five. Trin. asaphoides (Murch. /. c. Fig. 6) is probably a specimen of T. ornatus, in which the margin of the cephalic shield is broken away. If this conjecture be correct, the caudal shield would be more shortly triangulai', but the axis would likewise be many-jointed, having perhaps from ten to eleven lateral ribs. Possibly, however, the body thus referred to may be referable to the species last described. N.B. Both the former species and the present occur, but rarely, at Builth in the Llandcilo flags, and in Bohemia. Count Sternberg's specimens were found in a rock very much loaded with pyrites, in the district between Zebrak and Proskales, in Bohemia. Similar fragments have been found in the calcareous conglomerates of Carlshütten and Beraun. These have been figured by Zenker, (Beitr. Table IV, Fig. N, 5) ; and partly from these, partly from the caudal shields of quite a different species, the author has composed his Otarion deffractum. This genus Otario/i must be banished from the list of Trilobites. 5. T. tessellatus : Limbo seuti cephalici parabolico, tesselato-punctato ; scuto caudre triangulari. Long. }^". Cnjptol. tesseU. Green, Mon. 73, Fig. 4 ; and Model, No. 28. Bronn, Lefli. i, 117, 105, Table IX, Fig. 13. Emmr. Bisserf. 50. 2. Harlan, Zool. Res. 304. To judge from the impression, and from plaster casts, this species is more oblong and smaller than the others ; the form of the cephalic shield more parabolic, the lateral lobes of the rings of the body more arched, the caudal shield trilateral, rather acuminate. Occurs .in a black limestone of Trentonfalls and Glenfalls in New York ; also on the Island of Montreal. Remark. — Neither representation nor description indicate any more definite differences, and I therefore consider the species as uncertain. The same may be said with still greater reason of T. Bigsbyi (Geology of the Island of Montreal, in Lye. of Nat. Hist, of New York, p. 214; and Green, /. c.) and Nidtainia concentricu Eaton, (Geolog. Text -Book), both of which I consequently jiass over. OF THE SPECIES. 59 Genus 2. — Ogygia, Brongn. Cephalic shield semicircular or parabolic, flat ; the glabella moderately convex, con- tracted towards the posterior part, with three slight lateral impressions; cheek -shields lengthened into a more or less extended posterior angle. Eyes moderately arched, semicircular, affixed centrally beside the glabella. Facial suture very distinct, running in an arch towards the left and right, parallel with the anterior margin, between the latter and the glabella; then turning almost at a right angle towards the eye, forming the well-known plate above it ; and then with a curve in the shape of the letter Sj turning towards it parallel to the posterior margin in the principal direction, and terminating there at about three fifths of its extent from the glabella. Body certainly composed of eight joints,* the joints short, but tolerably broad, yet less by one half than the lateral lobes ; the latter straight, flat, bent strongly backwards at their extremities, and pointed. Caudal shield corresponding with the cephalic shield, its axis as long as the body, many-jointed, its sides furnished with radiating furrows, the interstices of which are again divided by smaller half rays. Locality. — In the oldest fossiliferous rocks. Remark. — This genus stands in so remarkable a degree of affinity to the preceding, that the circumstance of its hitherto hanng frequentl}' been confounded with the perfectly heterogeneous species of Asaplms is truly surprising. It is elf ar that even acciu-ate observers, as Emmerich and Boeck, have not always estimated correctly tlie zoological position of these fossils. 1. O. Buchii : Scuto capitis caudasque semicLrculato ; iUius angulis posticis acuminatis. Long. 3-5". Table 1, Fig. 2. Lhwyd, Phil. Tr. vol. xx, 279, tab. add. Fig. 15. Iclm. Brit. Ep. i, Table XXII, Fig. 4, {see Brunn.) Tril. dilatatus, Brunn, Kjobeuh. Wiclcnsk. Selsk. Sriff. 1781, i, 393, IV. Parkinson, 0/y. Bern, etc., iii, PI. XVII, Figs. 13, 15 (?). As. d. Dalm. Palcead. 67. 8, Tab. Ill, Fig. 1. Emmr. Diss. 28. 5. Sars, Ms, 1835, 336, Table VIII, Fig. 5. Isot. dilat. Milne Edw'ards, Crm. iii, 302. 9. Ascqi/i. de Buchii Brongn. Cr. f. 20. 2, Plate II, Fig. 2, A, B, C. Schloth. Nachtr. ii, 34. 8. Dalm. Palcead. 68. 9. Murch. Sil. Syst. ii, 662, Plate XXV, Figs. 2, 3 (young). Emmr. Diss. 28. 5. Milne Edw. Crust, iii, 309. 5. Cephalic shield nearly semicircular, but the longitudinal radius a little shorter than the transverse, furnished at each side with three slight transverse impressions, by which two anterior smaller lateral lobes, and a third posterior broader lateral lobe are indistinctly bounded ; the posterior margin is rather distinctl}^ turned up. Eyes not large, semicircular, corresponding in their position to the two anterior smaller lobes of the glabella. Cheek-shield with a concentric canal-like groove towards the exterior margin, and wdth a strongly prominent posterior angle, which in smaller specimens reaches * Quenstedt defends the se\ cn-jointcd figures, which were represented from defective specimens ; but all the well-preserved specimens that I have seen have had eight rings. 60 SYSTEMATIC ARRANGEMENT to the third, in larger to the sixth abdominal ring. Body distinctly furnished with eight joints, sometimes owing to the dislocation of two successive rings appearing to be limited to seven (see Remark 2); the rings narrower than the half-lateral lobes, moderately arched; the lateral lobes quite flat, at the end arcuated, curved towards the posterior part, with a strong diagonal furrow, which, however, does not quite reach to the terminating angle. Caudal shield formed like the cephalic shield, but its longitudinal radius larger than the transverse, therefore approximating to the parabolic form ; the axis gradually reduced towards the posterior part, rounded off at the end, distinctly articulated, the number of rings in it different according to age (usually thirteen), with a rather longer terminal joint ; in younger specimens the number is eleven, in older ones as many as seventeen ; the rays beside the axis on the shield usually fewer by about two than the number of joints of the axis ; thus, for example, when the number of joints is thirteen, exhibiting eleven rays, with slight traces of a twelfth, besides the two end joints, which are also indistinctly separated ; the intervals between the rays again divided by an oblique diagonal furrow, similar to the lateral lobes of the rings of the body. Remarks. — 1. Asaph, dilatatus and A. de Buchii of authors are probably the same species. The figure in Dalman's work is drawn from a cast, and owing to tins cii-cumstance is very indistinct, so that I have preferred the latter name, the species having been fii-st represented distinctly under that. Parkinson's, Brougniart's, and ^Nlurchison's distinct figures leave no doubt as to the identity of the species. Lliwyd's figure in the ' Philosophical Transactions' also represents this species tolerably well, for which reason it has been quoted by Brunnich from the ' Ichnographia Britaunica.' Individuals vary very much in point of size ; I have a caudal shield before me from the collection at Halle (No. 639), wliich is scarcely so large as a sixpence, having eleven joints in the axis, a pretty long undinded terminal joint, and ten rays. The number increases by the progressive division of this longer terminal joint with increasing age. Another specimen of the same rock (a blackish-gray grauwacke, locality unknown) was figured by me, and compared with perfect specimens in the Berlin Museum (Nos. 9.8 and 9). 2. Quenstedt adheres to the view that these Trilobites are seven-jointed, and founds his opinion on the figiu-es given by Dalman and Brongniart (3, A), as well as on original specimens. There are certainly two well-preserved fragments in the Museum at Berlin (Nos. 9.1, and 9.5), with only seven distinct joints ; but there are also others, equally distinct, with eight joints (Nos. 9.8, and 9.9) ; and the former number can therefore only be owing to a dislocation of two rings one under another. Con- sidering that the impressions arc merely those of shells, such a dislocation is very conceivable, and the more readily so, the less perfectly the shell had been preserved. The same remarks hold good with regard to the other species. 2. O. Guettardi: Scuto capitis caud;cque parabolico ; illius augulis posticis longissime acuminatis. Long. 3-6 inch, Table I, Fig. 3. Brogn. Cr.fo.'^s. 28. 1, Plate III, Fig. 1, A,B. Bronn, Leth. 1. 119, Table IX, Fig. 19. BucKLAND,Ä%. Tr. Plate XLVI, Fig. 9. Milne Edw. Crust. iii,337. 1. Dalm. Palaad. 72. I. Emmr. Diss. 27. 1. Tril. Gaett. Schloth. Petrf. Nacldr. ii, 93, and 35. 13. 0(iy(iia MurcMsoni, Murch. Sil Si/st. 664, Plate XXV, Fig. 3, a (the lower figure h does not belong to Of///f/ia, but to an Jsajj/ii/s). Milne Edw. /. c 338. 3. Cephalic shield olilong parabolic, rather pointed ; the glabella, as far as it can be recognized, formed as in the preceding species ; the eyes oblong elliptical ; the posterior angles of the cheek-shield as long as all the rings of the body together, or even longer. Eight body rings, their transverse diameter larger than half the breadth of the lateral lobes. OF THE SPECIES. 61 both of which are relatively longer than in the preceding- species. Caudal shield oblong parabolic, rather pointed, with a broad axis, which reaches to only three fourths of the length of the shield, and consists of nine rings ; the lateral parts furnished with eight radiating furrows. Occurs in the blackish-gray clayslate of Angers, in specimens in the Berlin Museum (No. 10. 1). Renun-ks. — 1. There is no figiu-e of this species in Gucttard's 'Treatise on the Slate of Angers' (Mem. fie TAcad. de Scieuc., 1757, p. 82), or at the most it is only the figure marked 3, in Table VII, (V), that could be considered as such. 2. Murchison describes several Tiilobites in his work, which have been taken for Ogtji/ia by other authors,, but which do not belong to this genus. Asajikus corndensis (G63, PI. XXV, Fig. 4) certainly approximates in many respects to O. Buchii, but is probably a genuine Asajj/ius ; at least, this is the case if the lateral lobes of the rings of the body ha\e been con-ectly represented. A. duplicatu.i, (ibid. Fig. 8,) on the other hand, is probably only a flattened caudal shield of Oijijgia Buchii, in its young state. The figui'es of Asaph, tyrannus (G62, PI. 'XXIV and XXV, Fig. 1) do not belong to Ogyyia, but are also to be referred to Asuphus. 3. Ogygia Desmaresti, Brongn. I. c. 28. 2, PI. Ill, Pig. 1 ; Schlote. Nachtr. 23. 2, and 35. 14 ; Dalm. Palaad. 72. 2; Milne Edw. Crust. 338. 2; Emmr. Dm. 27. 2. The impression of a fragment from the lower side presents too few characters to enable one to found a separate species. The specimen perhaps only belonged to a very large specimen of the Ogygia Buchii, the rings of which are partially pushed one above another, and for this reason appear small. It certainly belongs to Ogygia. Guettard's figures, which are quoted by Milne Edwards, relate to quite a diflereut species, namely, my Ilhenus giganteus. Division B. Trilobites having a simjjle, though tolerabig large caudal shield, the axis of which consists of but few joints, and is always .shorter than the body. The genera belonging to this division may be divided, according to the number of body rings, into eight jointed and ten jointed. First Subdivision (a). Eight-jointed Trilobites with a short articulated caudal a.xis, incapable of rolling them- selves up. — Odontopleurid.e. Genus 3. — Odontopleura, Emmr. (Acidaspis, Murch. ; Ceraurus, Locke). This remarkable genus is closely allied in habit to the preceding, and is highly interest- ing in a zoological point of view, because the two species are commonly distinguished from one another in the same manner as the species of the preceding genus. The cephaHc shield is subsemicircular, the longitudinal radius being much shorter than the other ; the moderately convex glabella is undivided in its length, contracted towards the posterior part, and furnished with a strong articulating varix ; it enlarges laterally, and at this point has three other little knobs beside it in two rows. The facial suture resembles that of Ogygia, forming at the anterior part an arcli before the glabella, then extending inwards to the eye ; thence turning to the posterior margin, and penetrating it at about one fourth of the distance from the terminal angle. 62 SYSTEMATIC ARRANGEMENT The cheek-shields are therefore broad, thickened at the entire exterior margin, pro- minent, produced beyond the anterior part of the central shield, and furnished with very small eyes above at their highest point, towards the posterior part beside the posterior margin of the outermost lobe of the glabella. The body-rings (eight in number*) are small, but strongly arched, and the lateral lobes are situated on one plane ; each has an elevated transverse ridge, and a long terminal spine directed obliquely and posteriorly. The caudal shield has a short two-jointed axis, only one elevated lateral rib, but large, strong, marginal spines at the exterior circumference. The surface of the body is regularly covered with tubercles and knobs. Locdihj. — In the upper Silurian and Devonian strata of the Eifel, Silesia, and England. 1. 0. ovata : Corpore ovate, dilatato, tmdique fimbriatim spinoso ; lobis trunci bispinosis, scuto caudae duodecies spinoso. Long. % inch. Table II, Fig. 11. Emmr. Diss. .53, adj. tab. Fig. 3 ; Batfics tubercuhttiis, Klöden, Verst. der Mark Brcnidoihiirr/, 112, Plate I, Fig. 16-23. This remarkable species occurs in a yellowish, liver-brown limestone, found as a boulder in Silesia by M. Bocksch ; the only known specimen was presented to the collection at Berlin by M. Dechen, and I am indebted to the latter gentleman for description and figure. The circumference is a broad ellipse, the transverse diameter of which is more than two thirds of the longitudinal diameter. The length of the cephalic shield occupies rather more than one sixth of it ; the glabella is smooth in the centre, granulated at the sides ; the two succeeding smaller tubercles beside it are minutely granulated, the third external one has three more considerable eminences before the region of the eye, and many smaller ones ; the cheek-shields are uniformly granulated, and their external reflexed margin is also ornamented with a row of tubercles and spines, which are visible everywhere except in the centre of the anterior extremity. There is a very large tubercle on the centre of the articular fold ; beside it at each side a rather smaller one, and surrounding the latter several very small ones. The axis portions of the rings of the body have two rather large tubercles beside the centre, and also two small ones externally at each side. An elevated fold is seen on the lateral lobes, which terminates at the margin in a spine, and which is covered on its surface with seven tubercles, alternately large and small. Towards the anterior as well as the posterior part of this fold we perceive a transverse row of other very small tubercles, and a second smaller row, corresponding with the anterior row, occurs at the margin before the spine. These small spines are all of equal length, but the larger ones become gradually longer towards the posterior part. The caudal shield is rather smaller than the cephalic shield, covered by larger or smaller tubercles, and spiny at the circumference ; the spines, of which there are six at each side, are equally long and equally broad ; the fold which proceeds from the first ring of the axis becomes bent at the third ring from the centre. * Emmerich only enumerates seven, but has omitted to notice the fact that both lateral lobes were broken off from the fifth joint, and that thus the true number was not given. Compai'c his figure and mine. OF THE SPECIES. 63 Remark. — Count Miinster's Tnnucleus yibbosus {Beitr. Ill, 47, Tabic V, Fig. 2") is probably a fragment of tlic cephalic shield of this, or of the following species. 2. 0. elUptica : Elongato eUiptica, lobis trunci unispinosis, scuto caudre dccics spinoso. Long. M". Table I, Fig. 4. Be/. — Faradoxides quatuor mucronatus, MuRCH. Sil. S^st. ii, 658, Plate XIV, Fig. 10. Acidaspis Brightii, ibid. Fig. 15.? Arges armatus, jiw. Goldf. Nova acta Ph. Med. Soc. Caes. Leop. Car. n. c. vol. xix, P. I, page 355, Table XXXIII, Fig. 1, d, e. In a gray limestone of the Eifel, according to a specimen in Sack's collection. Of the cephalic shield there is only a small portion ; but this resembles, as far as it goes, the cor- responding part of the preceding species ; the visible part of the anterior margin, however, is covered with thicker tubercles, and the lobes beside the forehead appear to me to be smaller. The rings of the body (eight) are all present, but only the last two are perfect ; on each there are two small lateral tubercles ; the lateral lobes are smaller than the double ring, each is furnished with two tubercles, and a long spine which issues from the fold ; I did not perceive a second anterior marginal spine. Caudal shield much smaller than in the preceding species, the axis furnished with two rings. The first sends forth a lobe-like swelling to the posterior margin, which terminates at each side in the fourth largest marginal spine ; the three preceding ones are successivel)^ smaller towards the anterior part, the two most central ones (the fifth of each side) as large as the second. Remarks. — 1. It is quite certain that the figui-e given by Goldfuss belongs to this species; and is too much unlike his Aryes armatus to allow of its being considered the same species. Murchison's Fig. 10 likewise undoubtedly represents this species, but it must still remain undecided whether Fig. 15 is the cephalic shield, as Emmerich and I consider it. 2. Several authors have recently described Trilobites, which belong to this group of Odoiitop/eum. First of aU, Mr. Locke {Sillim.. Am. Journ.) has described a Ceraurus crassatus. The fragment of Arges radiatus, copied by Goldfuss [Leonh. and Bronn), shows a great similarity with the maxillary shield of this species ; and it also corresponds with the maxillary shield of another species, Ceraurus crenatus, of which Dr. Loven (Ofveis, &c.) has given an elaborate description. The body in the latter, however, consists of niue rings, which denotes a considerable, and even generic difference. Ceraurus globiceps (Portlock, Geol. Rep. of Londonderry , &c.) can with less certainty be identified with the genus we are now considering ; it seems rather to have affinit}' with Ceraurus pleurexanthemus (Green), a species which is supposed by myself and Dr. Beyricli not to be connected with Odontopleura. Genus 4. — Arges, Goldf.* As I am not acquainted with this genus from actual investigation, I shall here give an abstract of Goldfuss's description. Cephalic shield highly arched ; at the centre of the glabella there are two very high, reflexed, diverging spines ; the sides behind the checks are hkewise furnished with a spine, the margin is narrow, the posterior part prominent in an angle, rather curved, equal in length to the joints of the body. Below there is a prominent mouth-plate, much turned downwards, which incloses semicircularly the most anterior part of the head behind the * The name of the genus is not well chosen, as there is aheady a genus of Acori described by G. Fischer under the name of Aryas ; other names of the same author arc also subject to similar objections. Harpes reminds one too much of Harpa or Harpte, and Fabricius had already used Brontes for a genus of beetles. 64 SYSTEMATIC ARRANGEMENT margin (the Clypeus). The eyes and facial suture cannot be distinguished. The body is pro- bably furnished with eight joints (only seven rings are distinctly represented in the figure) ; the rings and the lateral plates are highly arched and broader towards the posterior part ; the diagonal diameter of each ring is greater than the width of the lateral lobes ; the latter terminate at the margin in a spine ; the separate rings are successively broader and larger towards the posterior part. Caudal shield large, with an almost simple, apparently unarticulated axis, upon which is placed a long spine, bent backwards ; the external margin furnished with spines alter- nately large and small, the sides with indistinct radial folds. The whole surface is finely granulated, there are large tubercles on those parts of the circumference whence spines spring. Locality. — In the transition limestone of the Eifel. The only known species is A. armatu», GoLDFUSS, Nova acta Pki/s. Med. Soc. Ca.s. Leap. Carol, n. cur. vol. xix, PI. I, p. 355, Table XXXIII, Fig. \, a, c. Entire length two inches, the body about ten lines. The granulation appears to be uniform, it forms a diagonal row of larger tubercles on the rings and lateral lobes, accompanied also by smaller ones. The caudal shield exhibits radiating folds, which turn towards the larger spines of the margin of each side ; between the first and second of these spines there is one smaller spine, between the three following there are always two ; the two most central principal spines immediately at the end have no smaller spines between them. Second Sitbdivisio» {h). Ten-jointed Trilobites with a short articulated caudal axis. Animal not able to roll itself into a ball. Genus 5. — Bronteus,* Goldf. (Goldius de Koninck). The caudal shields of this genus are common enough, but all the other parts are so rare, that I have never had an opportunity of observing them. The character of the group may possibly therefore be defective. The cheek-shields are always broken off from the cephalic shield, whence -Goldfuss inferred their actual absence, which to me, however, does not appear probable ; the remain- ing part has a highly reflexed margin both before and behind, and a depressed glabella joining the margin anteriorly. The glabella is divided by lateral bent intersections into four lobes, which are successively smaller from the antei'ior to the posterior part, and con- tracted at the third and fourth lobe. The facial suture, which, in my opinion, borders the cephalic shield on both sides, issues at the anterior part from the margin near the angle of *Dr. Beyrich has recently communicated additional information concerning this genus, in his treatise on ' the Trilobites of Bohemia,' and has endeavoured to determine the distinction of the species move accurately. He proves tliat some species possess a granulated and others a lineated surface of shell, and further distinguishes them according to the number of furrows at each side of the caudal .shickl, which amount to either six or seven. OF THE SPECIES. C5 tlie glabella, runs on both sides rather cui-ved towards the eye, wliich scorns to be situated beside the narrowest part of the glabella. It then forms over it the well known covering-plate, and turns itself with an S-shaped curvature towards the posterior margin, where it seems to terminate not far from the external angle. The ten rings of the body are short, almost as broad as their lateral lobes, and are diagonally arched; the lateral lobes towards the exterior part are flat, with a strong curvature backwards. The caudal shield is very large, circular, or slightly parabolic ; it contains at the anterior part a very short one-jointed axis, from which radiating furrows and broad ribs proceed to the sides. Locality. — In Devonian and upper Silurian strata. 1. Br. flabellifer : Superficie tota graruilata; costis scutae caudalis quindecim, sulcis latitudine sequalibus, serie granvilorum majorum uotatis. Long W^-^Yi". Ä^— GoLDF. /. c. 361, Fig. 3. Leonh. u. Bronn. JaJir/j. 1843, 349. 3. Tab. XYII, Fig. 3. RoEMER. Ferst, d. Harzes. 37. 1. Tab. XI, Fig 1. The granulation on the cephalic shield consists of tolerably large tubercles, between ■which there are some very small ones ; the rings of the body and lateral lobes have a diagonal row of tubercles ; the almost circular shield exhibits fifteen elevated ribs, which are divided by nearly equally broad intervening spaces, and on each rib there are many nearly equally large tubercles, three or four together, the central being largest and most prominent. The centre of the entire shield is convex ; it becomes flattened towards the margin, and expands into a horizontal border. Remarks. — Count Münster has figured [Beitr. z. Petref. iii. Tab, V, Fig. 13) several fragments which belong to caudal shields of Bronteus. Fig. 13, B. radiutus, Fig. 15, B. subradiaius, appear to me hardly to differ from B. flabellifer. Fig. 14, B. costatus, Fig. 16, B. Neptuni, have a longer axis. The former has the same number of ribs as the species now ])eforc us, but is very different in size and structui'e. The latter [B. Neptuni) seems to approximate to Ent. laticauda, Wahl., in its nine flat ribs. 2. Br. laticauda: Superficie glabra, transverse lineata; costis scut» caudalis tredecim, latis, planis. Long. ? Ä//.— Wahl. N. Act. Ups. viii, 28. 3. Brong. Crust, fos. 24. 5, PI. Ill, Fig. 8. ScHLOTH. Petref. Naehtr. ii. 22. 5. 35. 12. Dalm. Paland. 52. 13. and 71. 18. Beyrich, Böhm. Tril. 42. 4. f. 8. 9. Wahlenberg described specimens obtained from a white limestone from Osmundsberg, in Dalecarlia, and the fragments which I examined in the Berlin Museum (Nos. 7. 1-4.) were heaped together in a ver)' similar deposit. The cephalic shield consisted as usual of a single central piece having an anterior and posterior strongl)' reflexed margin, the former being narrow and strongly curved, the latter rather broader, but less strongly arched. The curvature may have corresponded with the rings of the body. A stamp-shaped, slightly lobed glabella occupied the whole central part, and became broader at the anterior margin laterally. Close to it at each side the nearly circular cheek portion arched itself, and at the posterior margin of this a covering plate for the eye seemed to be indicated. I did not find any cheek-shields. Tiic caudal shield was more parabolic, had a nearly equilateral 9 66 SYSTEMATIC ARRANGEMENT triangular axis and thirteen narrow flat radiating ribs, six on each side of the odd central one. Of these ribs the odd one only (left at the end) is straight ; the other six pair, the symmetrical lateral ones, are somewhat curved in the shape of the letter S- Remarks. — 1. Wahlenberg, in the place already quoted, has figured a fragment which does not belong to the genus Bronteus. The caudal shield also does not resemble accurately the one I have described, for it has only nine short broad ledges, which, however, are so unsymmetrically ai-ranged that they are of themselves sufficient to convince us that the drawing is erroneous. I do not ventiire to decide whether Count v. Miinster's B. Neptuni (see remark on the last species) belongs to the present form. 2. The genus Lic/ias of Dalman [Palaad 53, iv, and 73. Entomostr. laciniahis. Wahl. /. c. 34. 8. Tab. II, Fig. 2. Brong. /. c. 35. 3. PI. Ill, Fig. 3. Schloth. Nachtr. ii, 36. 19. Milne Edw. Or. iii, 344. 3), which appears to me most nearly allied to Bronteus, I am obliged to omit, because the fi-agments that have come under my obsei-vation exhibit nothing to characterize it.* Division C. Trilobites havi/u/ a simple but very small eaudal shield, the ax-is of which is many-jointed, hut vJiich is always shorter than the body. OleniDjE. The two genera, Paradoxides and 0/e/ius, belonging to this division have been hitherto united by the authors, but are distinguished readily and safely by the caudal shield, which in Paradoxides has no lateral enlargement at the base, while in Olenus, on the other hand, it is enlarged at that region, and thus generally assumes a trilateral shape ; the former genus has from sixteen to twenty, the latter fourteen body-rings. Genus 6. — Paradoxides, Brongniart (Olenus, Sect. I, Dalman). Cephalic shield lunate, with a thickened but not reflexed mai-gin ; the glabella clavate or oval, moderately convex ; enlarged anteriorly, divided into four portions by three curved sutures, of which the posterior is the margin of the articulation with the body. The lower part of the head (PI. I, Fig. 7, Ent. bucephalus — Wahl, et auct.) has a less prominent boss, analogous to the anterior division of the upper part, which diminishes posteriorly, and is terminated by a convex reflexed margin, having at each side an oblique transverse impression. The facial sutures are nearly parallel in their principal direction, commencing at the anterior margin on a line with the eyes, turning towards the eye with an S-shaped curvature, forming a slightly arched lid, and returning in a similar S-shaped curve towards the posterior margin. Eyes oblong, lunate, depressed, corresponding with the second division of the glabella, reaching towards the anterior part nearly to the centre of the first division, and towards the posterior margin rather beyond the commencement of the second ; eyelid rather more convex than the neighbouring part of the cheek. Cheek-shield narrower than half the width of the cephalic shield, having a curved * Portlock, Lovon, and Beyrich have since published descriptions which give a tolerably perfect idea of this form. It appears from their accounts that Dalman's Ampyx ? pac/iyrhynchus, Green's Paradoxides Bottom, Castelnau's Platinotus and Actinurus, Eichwald's whole genus Metopias, and Portlock's Nuttainia Mbern'ira, all belong to one genus, which ought to retain its earliest name of Lic/ias. Dr. BejTich has undertaken to describe the species. OF THE SPECIES. 67 groove before the lateral margin, which ini])rcssion is continued posteriorly, and returns into itself at the posterior margin of the cephalic shield ; the external border is slightly convex, and produced at the posterior part in a long slightly incurved spine. Body many-jointed, apparently only having a definite number of joints in tlie separate species (16-20), the joints towards the posterior part gradually more narrow and shorter, the lateral lobes at first produced diagonally, and in this part almost as broad as the rings of the body ; afterwards projecting in a long angle turned outwards and backwards ; a deep diagonal impression on the transverse portion, which extends from the most anterior and innermost angle backwards, to the origin of the spine. Caudal shield circular or oval, without (?) lateral lobes and enlarged sides at the base, with a short but articulated axis, and a flat border to the posterior portion. Localitij. — In the oldest Palaeozoic strata (grauwacke, clayslate, and alumslate) ; hitherto only found in Bohemia, Sweden, and near St. Petersburg. Remark. — I know onlj' two distinct species of this genus from my own observation, and confine myself here to the description of these two, but in so doing would not be understood to question the propriet}'' of tlie others to rank as species. Naturalists having an opportunity to investigate perfect specimens of the species which I have not admitted, will be able to decide how far they really differ from the two here enumerated. 1. P. Eohemictis : Protuberantia capitis clavata ; anguUs scuti cephalici dimidio corpore longi- oribus ; trunco \acies annulate. Long. 1-6." Vur. juveii: annulis trunci 18; lobo lateral! secundo in spinam longissimam extenso. Tab. I, Fig. 6. Ref. — Oleiiiis pi/mmidaUs, Zenker, Beifr. etc. 41. Tab. IV, Fig. T. U. V. Tril. gracilis, BoECK, Magaz. f. Naturw. I, Fig. 15. Sternberg, Verh. d. Vaterl. Mm. 1825, Tab. I, Fig. 4, C, and 1833, p. 47. yEfafe paulo provectiorQ) Tril. minor Boeck, 1. c. f. 12, 14. Var. senilis: annulis trunci 30; lobo lateral! secundo reliquis aequali. Tab. I, Fig. 5. Tril. bohemicus, Boeck,/. c.f. 2. Sternberg,/, c. 1825, 83. Tab. I, Fig. 4. A. B. 1833. 46. KiNSKY, \nBoriis Abha7icll. etc. I, 246, Fig. 4, 5, 7. ?'. longicandatus, Zenker, Beifr. 37, Tab. 5, Fig. A to F. Emmr. Diss. 48. 4. Milne Edw. Cnist. iii, 341. 2. Olenus Tessini, Var. 1. Dalm. Palaad. 73. Central part of the cephalic shield rather quadrate, but the distance between the eye-plates rather greater than the longitudinal diameter ; the anterior round lobe of the glabella longer than the three others together. Spines of the maxillary shield longer than half the body ; the spine of the second ring of the body as long as this during the youth of the animal, gradually getting shorter, and finally reduced to the same length as the spines of the other body-rings. Rings of the body less numerous during youth (sometimes sixteen, usually eighteen), at a more mature age probably always twenty (at least I have never seen a greater number in perfect specimens). Caudal shield quite oval, rather broader towards the posterior part, almost flattened, the axis inarticulated during youth, afterwards one- jointed, at maturity furnished with five joints. Locality. — In a blackish-green grauwacke of Bohemia, near Horrowic and Ginec ; also in Norway and Sweden, in the latter in alumslate, at Olstrog, Dämmen and Carlsfors. Remarks. — 1. 01. pyramidalis, Zenker {Tril. gracilis, Boeck) I can only agree with Count Sternberg in regarding as a young specimen of the Tr. lonyicavdufus and Tr. bohemicus of the same author, and 68 SYSTEMATIC ARRANGEMENT this view is supported uot only by the relative proportions of the body which perfectly coirespond, but also by the delicate nature of the covering, and the long slender spines. The remarkable prolongation of the second lateral spine (uot the third, as Boeck and Count Sternberg have already correcth' shown while controverting Zenker) indicates some peculiarity relative to the young age of the animal (at least so far as it seems to have formed a pair of forceps with the long spine of the cephalic shield). The length in this case gradually decreases as the others increase, but is still distinctly visible in individuals that are half grown. I look upon Tril. minor, Boeck, as an instance of this kind. That the rings of many-jointed Ciiistaceans increase in number as the animal grows, and that this number is only com- plete when the animal is fully gro^v^l, is a fact too well known to the natm'alist to require proof in this place, but on this suljject I would refer to my own investigation of the Phyllopoda, and the elaborate and new observations of Zaddack and Joly. [Ann. des Sc. n. s. 1840 and 1842.) Olenus latus (Zenker /. c. Figs. W, X. Mune Edw. /. c. 441, 3) is distin9tly the same species as the one above described, and is merely flatly compressed. 2. The species Paradoxides seu Olenus Tessini (Entom. paradoxissimus, Linn. Mus. Tess. 98, Tab. Ill, Pig. 1 ; Wahl. Nov. act. Ups. viii, 34, Tab I, Fig. 1 ; Brongn. Cr.f. 31, PI. IV, Fig. 1 ; Schlot. Pet. Nacht, ii. 23. 1. 35. 15; Dalman, Pal. 54. 1. 73. 1. Tab. VI, Fig. 3; Boeck, May. f. Nat. I. 26; Bucklaud, B. T. PI. XLVI, Fig. 8; Bronn. Leth. 1, 120, Tab. IX, Fig. 16; Quenstedt, Wieg. Arch. 1837, 348; Emmr. Diss. 48; Milne Edw. Cr. iii. 340, 1, PI. XXXIV, Fig. 11 ; Hising. Leth. suec. 18, Tab. IV, Fig. 1) appear to me, judging from the representations and descriptions enumerated above, to be scarcely different from P. bohemicus ; at least I find no certain and available difference. In Linnseus's oldest figure there have been indicated at most seventeen body-rings, and the caudal shield has here been distinctly represented without lateral lobes. Wahlenberg represents twenty-one such rings, and twenty-two lateral lobes, the last pair of which is affixed to the caudal shield itself. Dalman's figure represents a similar caudal shield, but onlj' twenty body-rings ; and both authors state that they have only examined imperfect fragments, and make out no more clearly the caudal shield. Brongniart copied from Wahlenberg ; Bucklaud, Bronn, Milne Edwards, and Hisinger from Dalman. I consider therefore the figure given by Linna3ixs of tlie caudal shield, and Dalman's enumeration of the body-rings to be correct, and I thence infer that P. Tessini is specifically identical with P. bohemicus. 3. Wahlenberg (Tab. I, Fig. 7) has figured the impression of the under side of a cephalic shield (the hypostoma) as a distinct specific form, under the name of Entom. bucephalus (I. c. 37. 10, Tab. I, Fig. 6). Following in his footsteps, we find Dalman {Pal. 55. 2), Schlotheim {Nacht, ii. 37), Boeck {Mag.f. Nat. I, Fig. 16), Milne Edwards {Cr. iii, 341), and Hisinger (/. c. 18) expressing the same view more or less doubtingly. More recently Sars {Isis 1835. 342), Quenstedt {Wieg. Arch, 1837, I. 349), and others, have recognized the identity of the structure with that of P. bohemicus, and M. v. Buch has shown me some specimens which show the fact in a very instructive manner. I have figured such an under cephalic surface in Tab. I, Fig. 7. The concentric lines there visible may be observed in all under surfaces of Trilobites, and have ah-eady been alluded to by Zenker, in the work already cited. Figs. C. D. P. spimdosus : Protuberantia capitis parabolica ; augulis scuti ceplialici dimidio corpore brevioribus, trunco sedecies annulato. Long. 1". ^,y._LiNN. Jrf. Holm. 1759, 22, Tab. I, Fig. 2. Wahl. N. a. Vps. viii, 38. Tab. I, Fig. 3. Brong. Cr. /. 32, PI. IV, Figs. 2. 3. Schloth. NacMr. II. 25. 2. 36. 16. Dalm. P«/. 56. 2. 73. 2, Tab. V, Fig. 2. Emmr. Z»/.«*. 47. 5. Quenstedt, Wiey. Arch. I. c. 349. Milne Edw. Cmsf. iii. 342. 5. Hising. Ldh. Suec. 19, Tab. IV, Fig. 2. I have seen only a few and not very distinct specimens of this species, but these cor- responded with Walüenberg's and Brongniart's figure in tlie principal points. The cephaHc shield exhil)its a glabella which is not broader anteriorly, but is gradually rounded towards tliat part, with three slight impressions at each side. I counted sixteen rings in the body. OP THE SPECIES. 69 tlie exact number which seems to have been seen by Dahnan, whilst seventeen have been given in his and Wahlcnberg's figure. Brongniart's very excellent figure exhibits also sixteen, probably the correct number. The lateral lobes of the first body-rings are very broad, broader than the axis, but they rapidly get smaller posteriorly, so that the last become narrower than the axis. The caudal shield is small, roundish, transversely elliptical, and has no lateral lobes. Local if J/. — The same as F. bohemicus and P. Tessini ; and also in the clayslate of Angers, associated with Oyyc/ia Gunttardi. (Vide Guettard, Mem. de I' Acad des Sciences, torn, xiv, ann. 1757, PI. VI, 8, Figs. 3. 4. 5.) Remarks. — Various species hitherto impci'fectly kuowu appear to belong to this genus. Among these are — - 1. A figure bv Count Razoumousky, in the Annales des Sciences (t. viii, PI. XXVIII, Fig. 11). While possessing a similar structure with 0. bohemicus, this specimen is distinguished by a long spine at the extremity of the caudal shield. Locality. — In Silurian strata between St. Petersburg and Lake Ladoga. 2. Paradox. Boltoni, Bigsby (Green, Mon. 60, f. 5, Joum. Ac. N. S. of Phil. vol. iv, p. 365, PI. XXIII. Harlan, Zool. res. 303. Milne Edw. Crust, iii, 314, n. 1). This genus, as we have already seen, belongs to the genus Lichas, Dalman. See Remark 2, under Bronteus laticauda. 3. Cahjm. actinura (Dalman, K. V. Ac. Hand. 1824, 370, Tab. lA^ Figs. A, B, C. Hising. Leth. suec. 11, Tab. I, Fig. 7. Milne Edw. Crust, iii, 321). A species having fifteen (?) lateral lobes and body-rings, and resembling so closely in every respect P. Boltoni, that I cannot but refer them to the same genus, intermediate between Bronteus and Paradoxides, the chai'acters of which canuot yet be determined with certainty. 4. Parad. Harlani (Green, Silliman's Am. J. of Sc. and Arts, vol. xxv, p. 336. Harlan and Milne Edw. as before cited). 5. All the other species hitherto iucludcd among Paradoxides or Olcnits, probably belong to the following genus. Gcii/fs 7. — Olenus (Paradoxides p/Olenus Aucfonim). Cephalic shield constructed as in Paradomdes, but comparatively bi'oader and shorter ; the glabella parabolic, not broader towards the anterior part, but rather more narrow and rounded, at each side furnished with three slight furrows, which separate it into four divisions, of which the posterior narrow one is articulated with the body. Eyes oblong curved. The facial suture originates at the anterior margin, in the region of the eye. It is there bent at an angle, and returns nearly parallel to its former direction towards the eye, where it makes a bent plate, and passes in an S-shaped curve towards the posterior margin, where the two sutures gradually and continually diverge. Cheek-shield tolerably broad, with a reflexed margin, and with a pointed but not very long posterior angle. Axis of the body many-jointed (fourteen ?) ; the joints more narrow tlian the lateral lobes, short, and moderately convex; the lateral lobes extended in a straight line, only terminating at the end in a short point directed backwards ; each furnished with a diagonal furrow from the anterior and internal towards the posterior and external part. Caudal shield much broader than long, semicircular, straight at the anterior part, arched or obtusely angular, trilateral posteriorly, with a distinct articulated axis. Localifi/. — In very old strata with species of the preceding genus. •70 SYSTEMATIC ARRANGEMENT 1. O. (jihbusiis : Scuto capitis inter suturam facialem et umbonem tuberculo transverso signato ; rhachi coi-poris quaterdecies annulata, caudae quinquies. Long. 1". Table III, Fig. 9. Bef. — Tr. truncatus, Brunn. N. Act. Hafn. \, 391. Modeer in Berl. Gesellsch. Schrift. vi, Table II, Figs. 3-.5. Entom. gibhosm, Wahlenb. N. A. Ups. viii, 39. 12, Table I, Fig. 4. Brongn. Cr.foss. 35, PI. Ill, Fig. 6. Schloth. Nachtr. ii, 26. 4. 36. 18. Dalm. Palaad. 56. 4. 74. 4. Boeck, Mag. f. Nat. i, 24. Emmr. Dissert. 45. 1. Milne Edw. Crust, iii, 343. 4. Hising. Leth. suec. 19, Tab. IV, Fig. 3. Cephalic shield four times as broad as it is long, th& axis remarkably narrow ; an elevated elliptical prominence both to the left and right at the anterior extremity, the pro- minence extending as far as the facial suture.* The number of joints in the axis of the body is fourteen ; the lobes of the first joints are twice as broad as the axis ; those of the last only a little broader. Caudal shield semicircular; the axis five-jointed, with an anterior margin of articu- lation ; the lateral portions flat, without rays, the margin rather reflexed. Locality. — In the alumslate and stinkstein of Andrarum. Remarks. — 1. The cheek-sliields of the head are absent in all the older descriptions and figures, being always broken off. They are often present, however, near the other remains, so that there can hardly be a doubt about theii- existence. I counted fourteen body joints in the impressions of young and perfect indi\iduals. 2. Asaph, tetragonocephahis (Green, Sill. Am. Jo. vol. xxv, p. 336 ; Emm. Diss. 46. 4 ; Milne Edw. Cr. iii, 330) is so similar to 01. gibbosiis, that they are liable to be confounded with one another ; indeed I was not able to discover satisfactory specific distinctions in the plaster model which I examined at Berlin. I counted in this specimen fourteen body-rings, and certainly three caudal rings, but the latter were indistinct and imperfect. The species was found in the alumslate of Lockport. 3. Boeck, in Kielhaus's Gcea Norwegica (see Leonhard and Bronn, Zeitshr. 1841, p. 727), has characterized two species nearly related to 01. gibbosus, which I am not acquainted with, and therefore give them here according to his statement. O. alatus (/. c. No. 38) is nearly related to 0. gibbosus, but the glabella (which is the only part known) is proportionably much narrower, and the transverse prominence which issues from its anterior extremity does not extend in so straight a #iue, but is produced more backwards. O. latus (1. c. No. 39) is much larger than 01. gibbosus, and the piece (probably the space) between the glabella and eyelid is considerably broader. I do not think such differences in imperfect fragments can justify us in founding new species. 4. Emmerich's Pur. acuminatus (Dissert. 46. 2), which is said to be distinguished from 01. gibbosus by a more developed angularity of the facial suture before the eye, and by a bending of it inwards at the posterior extremity, also appears to me merely to indicate an individual difference caused by differ- ence of preservation, as this is easily accounted for in the impressions of tender parts. 01. gibbosus in other respects varies, like its allies, very considerably in size, according to the difference of age ; I have seen specimens of Wi" length, and others scarcely !^". 2. O.forficula. Sars, Isis, 1835, 333, Tab. VIII, Fig. 1. Milne Edw. Crust, iii, .343. 1. According to the figures, this species most nearly resembles Paracl. spitiulosiis in the iiabit of the head {im Habitus des Kopfes), but has a glabella somewhat broader anteriorly, and divided by two furrows into three nearly equal parts. A slight longitudinal impression appears at the anterior of these, and on the third there is a small tubercle. Behind it the * By its position this prominence justifies the assumjrtion that a small tentacle issuing from the glabella has existed beneath it in a cavity of the shield. OF THE SPECIES. 71 swelling of the margin makes a fourth division. The facial suture terminates as in Olcnus, and the terminating angle of the check-shield is elongated. The caudal shield is semicircular, straight at the anterior jjart, bounded by a curve at the posterior part ; the axis consists of five to six rings, and a fold proceeds from it towards the posterior margin, which there projects in a large spine. This is all that is known of the animal. Locality.— k calcareous blackish-gray alumslate of Rusielökbacken, near Christiania. Remarks. — 1. According to Boeck {Gcea norw. \, No. 18), tliis species is not properly placed here, but forms witli Ceraurus pleureocanthemus (Green, Mon. 84, f. 10; Bronn, Let. i, 117, Tab. IX, Fig. 12 ; Milne Edw. Cr. iii, 346) a distinct genus. It is very probable that this view is correct, but since I have not myself had the opportunity of examining the two species, I must leave the decision to others. No doubt, however, Ceraurus represents a form closely related to the Olenides. In Green's figure eleven body-rings and a broad caudal shield are represented, the latter bearing a spine on one side exactly hke that of O. forficula.* 2. Murchison [Sil. Sys. vol. ii, p. (558, Plate XIV, Fig. 8) has described a large caudal shield, to which he gives the name Paradoxides bimucrotiatus, and this in many respects seems to hold an inter- mediate place between the caudal shield of the last and of the next succeeding species. It is straight at the anterior part, nearly an inch in width, and fiu-nished with a three-jointed axis, over which there projects forwards one of the articulation. A fold proceeds to the margin from each ring, and the three folds, like the rings themselves, become smaller posteriorly, so that the free semichcular margin is furnished with six rather bent processes.! 3. O. scarabeeoides : Scuto capitis convexo, vertice non elevato sublobato ; scuto caudali utrinque tridentato, axi biarticulata. i?p/._BROMEL, Jcf. lift. Uj}.s. 1729. 521. //. 3, and page 528. 6, c Fig. Wahl. iV. J- ups. viii, 41. 13, Tab. I, Fig. 2. Brongn. Cr. foss. 34. 3, Plate III, Fig. 5. ScHLOTH. Nac//f. ii, 25. 3. 36. 17. Dalm. Palcead. 57. 5. Emmr. Bissert. 47. 6. Milne Enw. C/-. iii, 344. \, Pelf iira scarab. Antltes scarabcBoides, GoiiD f. Lecju/i. und Br. Jahrb. 1843, p. 544. Of this species I am only acquainted with some fragments of heads and perfect caudal shields, and from these I must declare it to be a species with which I am too little con- versant to judge M'ith certainty respecting its systematic position. The glabella resembles that of the first described species of this genus, but is relatively shorter, broader, more convex, and the indentations, which are similarly divided, are slighter. The existing part of the cephalic shield beside it is deeply depressed, and thereby indicates a very great convexity of the cheeks. I think I recognize a trace of the eyelid in the region of the first anterior sutui-e ; a distinctly reflexed margin is visible at the posterior part ; but I have never distinctly seen the anterior and lateral margin. The caudal shield has a short two-jointed axis, and a margin of articulation before the first joint ; it is extended on both sides more * A new species of Ceraurus has been described by Portlock {Rep. 257, Plate I, Fig. 7) as C. globiceps. t In his treatise ' Ueber einige Böhmische Trihbiten,' Dr. Beyrich has shown that this species of Murchison's, together with Tril. Sternberyi, Boeck, constitute a new genus, for which he proposes the name Chirurus. He describes four Bohemian species of this genus, and includes also in it Cuhjmene Sternbergi, C. propinqua, and C. articidata of Münster [Beitr. z. Pet. iii, 37, Tab. V) ; C. speciosa, Dalman (Pal. 74) ; C. ornala, Dalm. {Arsber. am nya Zool. Arbet. 134) ; Amphion gelasimsns, Portlock [Rep. 289, Plate III, Fig. 4) ; and Arge.i p/aiwspino.vi.t, Portl. (/. c. 272, Plate Y, Fig. 9) ; the two latter being probably the cephalic and caudal shields of the same species referable to this genus (Chinirm). 72 SYSTEMATIC ARRANGEMENT than usual posteriorly, and is there furnished with a deep transverse furrow before the straight margin, and is drawn out at each side into three pointed marginal processes, which are situated lower than the general surface, and which issue from the deflexed margin. Locality. — The alumslate of Andrarum. Remarks. — ] . Wablenberg, who states that he has seen a perfectly preserved individual of this species at Copenhagen, describes it as having twelve body-rings with very short lateral lobes, which are pointed towards the posterior part ; he has, however, represented the glabella and the caudal axis much too broad, and for this reason I am inclined to consider the body axis as also too broad. 2. Harlan [Med. and Phys. Rev. 400 et seq.) describes two new forms, nearly related to Par. scaratxcoides. He speaks of them as Parad. triarttirus (I. c. 401. 1, Fig. 5), and Parad. arcuatus (/. c. 403. 2, Figs. 1, 2, 3). Both are from the carboniferous striita (?) of Utica, in New York. They are imperfect heads, which certainly resemble the fragments of 01. scarabaoides, but which still require a further investigation as to their true organization. The author compares them with Triarttirus Beckii (Green, 3Ion. 87, Fig. 6), with which they certainly seem to be related. 3. I shall treat more particularly in the Appendix of Triarttirus Beckii and Trilobites Slernbergi, which probably belong to the Oleneides. 4. I beg once more to remind my readers that I have mentioned Paradoxides spinulosus, Olenus forficida, and Olen. scarabceoides, as species which are both imperfectly known to me, and the correct arrangement of which in systematic order I cannot guarantee ; this is still more the case with the other species of other authors, which I have only enumerated here hypothetically. GROUP THE SECOND. 77te lateral lobes of the hodt/-nngs not horizontally extended in their whole length, hut turned downwards from the centre, and not terminatiny in a point, hut with an arched and rounded extremity. Furrowed on the surface alony their whole lenyth. C.\mpylopleuri.* I am only perfectly acquainted with the first two of the three genera enumerated in this group ; they are recognizable by their smaller, semilunar, cephalic shield, by their fewer number of joints (twelve to fourteen), and by their simple, semicircular, caudal shield. The one, Conocephalus, has fourteen rings ; the other, EUipsocephahis, twelve. The third genus, Hmpes, has a very large cephalic shield, shaped like a horseshoe, with long posterior angles, and is stated to have twenty-eight rings. Genus 8. — Conocephalus, Zenker. Cephalic shield not unlike a half-moon, but the posterior internal margin only slighth^ bent. Glabella separated by a deep furrow from the lateral lobes, becoming more narrow towards the anterior part, divided by four furrows at each side into four lobes, and becoming broader from the anterior to the posterior part ; behind the fourth lobe there is a reflexed margin of articulation. The lateral parts, together with the cheek-shield, are highly convex, surrounded by a furrow and by a thickened margin. Eyes small, but certainly present ; partly fixed at the anterior part beside the angles of the glabella, partly at the centre of the sides. * The following generic names, and the names of larger groups thence derived, have been alread}- made use of to designate various tribes of Locusts. OP THE SPECIES. 73 The facial suture couimenccs at the anterior margin far towards the outer side, turns inwards with a curve towards tlie eye, forms a small covering plate, and then runs towards the posterior angle, before which near the inner part it penetrates the posterior margin. The angle itself is furnished with a short straight spine. Body fourteen -jointed, the axis narrower than the lateral lobes, very convex; the lateral lobes quite horizontal, of equal breadth, deeply sulcated in their whole length ; from the centre they begin to curve downwards almost at a right angle, and are rounded at the extremity ; they are separated at the base from the axis by a deep furrow.* Caudal shield semicircular, very convex anteriorly, with a five-jointed axis, and slight furrows on the sides. Localiiy. — In the grauwacke of Bohemia, at Ginu. 1. C. Sulzeri: Oculis juxta apicem tuberculi frontalis. Long. VA-V . Table I, Fig. 10. Ref. — KiNSKY, in Bom's Ahh. etc., I, Figs. 1, 2, 3. Triloh. Sidz. Schloth. Nachtr. ii, 28. 1, and 34. 5, Table XXII, Fig. 1. Dalm. Palcead. 75. I. Sternb. Verhandl. d. Vaterland. Mus. 1825. 81. 4, Table II, Fig. 1, A. Boeck, vI%. for Natur. Sc. Figs. 20, 21, Trilob. Zippii. Conoc. costafus, Zenk. Beifr. 49. 15, Table IV, Fig. G-K. Milne Edw. Crust, iii, 336. Syn.— Conoc. Suheri, Bronn, Lethaa, 1. 121. 110, Table IX, Fig. 15. Emmr. A'»?. 43. 1. QuENST. in Wieffm. ArcJiiv. 1837, i, 347. Glabella very much contracted anteriorly, and almost rounded ; before it, and behind the thickened margin, there is a peculiar transverse fold. Eyes small, situated on tubercles immediately beside the anterior angles of the glabella, whence the facial suture continues directly across the sides, dividing the narrow cheek-shield. Body rings and caudal shield not remarkable. 2. C. striatus : Oculis in medio partium lateralium scuti cephalici. Long. lJ^-2". Table I, Fig. 9. Äe/:— Emmr. Diss. 43. 2, C fig. Trilob. Sulz. var. Sternb. II, I, A, and Table I, Fig. 3. QUENSTEDT, /. C. 348. Similar to the preceding species in size, habit, and structure ; but the cephalic shield totally different. The glabella at the anterior part is broader, straightly truncated, and merely furnished with rounded angles ; there is no transverse fold in front of it. The eyes are more distinct, attached to the centre of the lateral parts of the cephalic shield, and bearing the same proportion to the facial suture ; but a sharp ridge extends itself towards them from the angles of the glabella. The cheek-shields are not narrow and elongated, but short and broad, and only reach half as far anteriorly as in the last species. Boeck was the first to point out the differences which constitute this a species, although Count Sternberg had previously observed it. By mistake, however, he confounded the * Zenker (/. c), and after bim Quenstedt and Emmericb, regard tbis furrow as the indication of an articulation or suture ; but since in every specimen the impression is merely that of an internal shelly surface, the indentation is more probably the impression of an elevated ridge, -nhich may have served for the insertion of the muscles of the legs. The analogy of all other Trilobites is against the existence of a suture. 10 74 SYSTEMATIC ARRANGEMENT names, regarding the true C. Siiheri as the new species. Quenstedt acknowledged the points of specific difference without noticing what had been done before ; and Emmerich at length gave the name. Genus 9. — Ellipsocephalus, Zenker. Cephahc shield similar in outline to that of the preceding genus, but quite distinct in construction, being flatter and without posterior prolonged angles ; the anterior margin also is not elevated.* The glabella is divided from the shield by a slight indentation, equally broad, rounded at the anterior part, without transverse furrows, and even without a posterior articular fold. Eyes oblong lunate, very narrow, and projecting outwards. Facial suture short, com- mencing at the anterior part at the margin before the eyes, and curving over them towards the posterior angle. Joints of the body twelve, the axis nearly as broad as the lateral lobes, depressed. The lateral lobes at first horizontal, rather flat, and almost without furrow ; then curved downwards, more deeply furrowed, but the furrow pointed inferiorly ; with an anterior surface transversely affixed, indicating a deficiency of power in the creature to roll itself into a ball. The extremity is thus rendered obtuse-angled. Caudal shield small, semicircular; the axis one-jointed. Locality. — The Palaeozoic rocks (grauwacke) of Bohemia. The only known species attains a length of about 1 M inches, and is E. Hoßi. Table I, Fig. 8. Ref. — KiNSKY in Bom's Abhandl. 1. 246, Fig. 6. TrUohites Hoff. Schloth. Nachfr. ii, 30. 2, and 34. 6, Table XXII, Fig. 2, a, h. Count Sternberg, VerhancU. d. ratal Mus. 1825. 83, Table II, Fig. 4, and 1833. 50. Dalm. Palcead. 76. 2. Boeck, Ma(/.f. Naturv. I, Figs. 14, 17, 19. Syn. — ElUjjsocephalus ambiguus, Zenk. Beitr. 51, Table IV, Figs. G, K. Milne Edw. Cr. iii, 344. JEllips. Hoßi, Bronn, Lethaia, 1. 122. Ill, Table IX, Fig. 18. Emmr. Dissert. 44, VI. 1. Calymene decipiens, König, /co/^ sect, i, 2, Table III, Fig. 32. Genus 10. — Harpes, Goldfuss. Cephalic shield very large, in the shape of a horseshoe, very convex in the centre, flatly expanded at the whole external margin ; the posterior angles long, and projecting beyond the centre of the body. The glabella is very prominent, oval, and does not reach to the anterior margin ; it becomes narrower at the posterior part before the margin of articulation, and is furnished with a double impression, which separates two elliptical lateral lobes from its posterior half; by the side of it externally there is also a slight trace of a third arch-like impression and lobe. Eyes indistinct, small, appearing in the shape of knobs at both sides beside the anterior half of the glabella. * The impressious occur iu two kiuds of forms ; some have uo elevated mai-giu, others only exhibit the impression of it as an indentation in the matrix. Accordiug to this, there seems to have been a reflexed margin only at the lower side of the cephalic shield. This appears to me to be the case also with regard to Conoceplialus. OF THE SPECIES. 75 Facial suture indistinct ; I can perceive only a slight indented arch, which issues from the place at which the border and central shield meet together. This line turns towards the eye-tubercle, and separating from the latter at the posterior part, makes another turn with a sharper curvature, over the posterior half of the sides to the angle, which is formed by the open posterior margin and by the lobes of the angle. Body many-jointed (above twenty), the axis very convex, narrowing posteriorly, but elsewhere quite as broad as the lateral lobes ; both these are short, the latter at first hori- zontal, slightly furrowed, bent much downwards at the end, and obtusely pointed. Caudal shield not known. Zow//(y.— Upper Silurian and Devonian strata of the Eifel, the Fichtelgebirge, Bohemia, and Ireland.* Remark.^. — 1. Of this genus I have before me only a single cephalic shield, but this is for the most part well preserved ; it lies in a yellowish, liver-brown limestone, probably the same in which is also found Odontopleura ovata, and has, like the latter Ti-ilobite, preserved its real shell, partially at least. This shell is punctated with little indentations at all parts where it has not been damaged, but the punctation is luieven, so that the largest indentations are situated immediately at the circumference of the real cephalic shield, where the flat border proceeds from it ; and they decrease in size from this point both towai-ds the inner and outer part. A fine mai-ginal ridge runs quite round the open margin of the border, and before it there is a row of larger indentations. The eyes are wanting in the speci- men I possess, but their places are indicated. 2. Count Sternberg first described a species of this genus as TrUobiles unyula {Verhandl. d.vaterl. Mus. 1833. 52, Fig. 1), in which at least twenty body rings were perfectly distinct. From this Goldfuss constituted the genus {Nova act. Phys. Med. Soc. Caes. Leop. Carol, nat. cur. vol. xix, p. 1, 358, Table XXXIll, Fig. 2, a, b, c), and gave a more accurate account of the organization, which was, howe\cr, ah-eady known. According to him there arc twenty-eight body rings. Count Älünster endeavoured to enrich the genus by new species [Bcitr. z. Pctref. Parts III and V) ; but it appears to me that he has often merely taken individual differences for specific characters. This is the more likely since all his specimens, as also those of Sternberg, probably consist of mere impressions, without any remains of the shell. At present, therefore, I can admit only the following species :t H. tmgula : Limbo scuti cephalici antice latiori, punctate ; punctis internis majoribus, foraminulosis. Long, sine corp. l>^-2", cum corp. 2-23^". Table I, Fig. 11. Otarion pygmaeum, Münster (/. c. V, 115, Table X, Fig. 11), appears to me to have been a very young, but mutilated indi-iddual; Otar. eleyans (ibid. I, Table X, Fig. 2) an older individual, but also mutilated; Harpes macrocephalus, Goldf. (/. c. 359, Table XXX, Fig. 2, a, b, c), and the figure given in this work, represent full-grown, perfect individuals. Goldfuss's description is detailed and correct ; and as my specimen is not so well preserved, I will repeat his words : "The inverted egg-shaped body is depressed, but the head is considerably elevated, and occupies more than a third of the length of the whole animal. Its circumference is semi- circular, and it is suiTounded by a broad margin, which at the anterior part is horizontally * Portlock [vuh Keport, &c.. Tab. V) has published figures which prove beyond a doubt that the genus Harpes belonged to that group of Trüobites capable of rolling themselves into a ball. It cannot therefore be brought iuto auy near relation with Trinucleus, as Portlock supposes, and as Loven has endeavoiu-ed to prove {Ofvers, &c. 105). t I no longer hold this view, and am now much rather inclined to regard both Portlock's species as perfectly distinct ; and I also am willing to admit at least two of Count Miiuster's species. That represented in Table V, Fig. 19, 23, is one of these ; and the other is that marked Fig. 20, 22. The former reminds one of Harpes Flanaganni, of Portlock (/. c. 268, Plate \, Figs. 5-7) ; the latter, of his H. Doranni (ibid. 267, Plate V, Fig. 4). Count Sternberg's figure more resembles the former than the latter species. 76 SYSTEMATIC ARRANGEMENT extended, but assumes a more vertical position at the sides, and terminates at each side in a point, which is produced posteriorly for three fourths the length of the animal. Its border is rather thickened, and forms (both on its upper and lower reduplication) an elevated bordering line. From this horseshoe-formed extension of the margin, the head rises ante- riorly and laterally with a somewhat steep elevation, and in the middle of the elevated part it has an oval protuberance in the manner of a forehead, which is surrounded by an im- pressed furrow, and which does not descend to the expanded margin. It forms a keel (a very slight one, Akc.) at its highest part, and exhibits a slight fold in front of the furrow on the summit. A small semicircular eye-tubercle is situated on each of the large cheeks, almost at the anterior extremity of this fold, and close to it. Even with the naked eye one can distinguish a somewhat larger round protuberance at the centre of this eye-tubercle, and two oval ones of the same size on both sides.* Behind them may be discovered, with the assistance of a microscope, other small tubercles in regular rows. "The head terminates posteriorly in a small protuberant half-ring, to which the joints of the central body are united. The protuberance of the forehead and the summit of the cheeks above the eyes, are smooth ; and it is only upon the furrow of the former that a few small granulations are perceptible. The rest of the surface of the head is thickly granu- lated, so that the boundary towards the smooth forehead is distinctly marked, f " The expansion of the margin is prettily ornamented by a row of larger granulations on the surface, both of its upper and lower plate, and as well at the external as internal margin (i. e. in the cast ; in the true shell there are corresponding indentations, and no granulations, Auc) " From the head to the side of the tail, twenty-eight segments may be counted, becoming gradually and uniformly shorter towards the posterior part. Whether there is also a small simple caudal shield without ribs, cannot be determined from the specimens before us. The high convex spine (the axis) occupies a third part of the whole breadth, and its segments are ring-shaped; the ribs, however (lateral lobes), have only a fiat longitudinal furrow, are closely united, and form a flat expansion at each side. Their short ends are obtusely pointed and bent downwards at an angle, so that the body exhibits a narrow border. The anterior ribs (lateral lobes) increase gradually in length^ as far as the seventh or eighth, and the rest become gradually narrowed again behind them. The spine is granulated, but the sides are quite smooth." The specimen in my possession has no trace of body rings ; but I suppose from the analogy of the cephalic shield that the rings of the axis were also without granules, and merely ornamented with punctiu'es, Auc. * These parts are absent in the specimen which I possess ; judging from the figure, I should suppose that only the two oval spots are real eyes, and that the warts are little prominences on the shell. This genus would otherwise be characterized by four eyes, two on either side. t Goldfuss is here describing an impression without the shell, in fact, a cast in which all the indentations of the real shell appear as protuberances and granulations. In the same way Count Münster describes young individuals for his Trinuclens. X The breadth is from left to right. OF THE SPECIES. 77 II. Trilobites having the poiücr of rolling themselves info a haU. The distinctive character of this second, more numerous, and principal group of Trilo- bites is to be sought for in the structure of the lateral lobes of the joints of the body, which at first are continued horizontally, but are afterwards more or less curved vertically downward. At the point of curvature there appears to be a kind of articulation between two successive joints, or, at least, there is a very accurate insertion of one into the other. The lobe from this point becomes broader outwards and downwards, ceases to be con- nected with the adjacent ones, and makes a turn, its anterior edge being directed obliquely inwards, to find room by the side of the next preceding. It thus has a surface somewhat turned forwards, obliquely placed, and gradually widening below, extending hence to the posterior margin of the lobe, and only leaving a very small space for the true upper or external side. This space also, the true external surface, gradually diminishes from the point of articulation of the two lobes, and extends to the posterior margin ; it is usually rather strongly arched, and divided by a diagonal furrow, which proceeds from the anterior angle, close beside the rings of the axis, and likewise bends towards the external posterior angle. The anterior sharper margin of this furrow forms at the same time the edge, at which the oblique, but always flat, anterior surface meets with the posterior or upper sur- face. When the animal rolls itself up, the lateral lobes were passed one under another from the point of articulation, each preceding lobe covering the oblique surface of the next so completely, that nothing could be seen of the roUed-up animal except the convex posterior portion. I shall henceforth always call the surface, which is covered during the rolling-up process, the anterior, and, on the other hand, the one which remains externally visible, the external part; the former being manifestly intended to be concealed, since it is usually covered by the parallel punctured furrows which are found in all Trilobites at the lower surface of the shell, where exposed. Such punctures are never absent in well-preserved specimens ; but the oblique diagonal furrow on the upper side of the rings, on the other hand, is deficient in some genera {lllanus and Nileus). The boundary between the rings of the axis and the lateral lobes is also more indistinct when such is the case. There are, however, other characters also more or less directly connected with the power of the animal to roll itself up. As such, we may enumerate — 1. The much lai'ger and more projecting eyes, a character which, since it is wanting in the previous gi'oup, has led to the assertion, that most of the members of this group were blind ; I have, however, recognized the eyes in almost all of them (except, indeed, Trinucleus), and thus refuted, I hope satisfactorily, the notion of blind Trilobites. 2. The tougher nature of the horny membrane. It is at least remarkable that this part is preserved in a fossil state in almost all the members of this group, while in the members of the former group it is only met with when the remains are found in limestones. The Trilobites of this second group, however, occur chiefly in limestone, and the preservation of their shell may therefore be owing to that circumstance. 78 SYSTEMATIC ARRANGEMENT 3. The fact that the size and shape of the caudal shield correspond pretty nearly with the size and shape of the cephalic shield. This is no doubt the case also in Ogyyki, and partially in Trinudeus, but less generally than in the present group. We shall rarely meet with forms in which the caudal shield is much smaller than the cephalic shield; and, on the other hand, we shall find some species in which the former is the greater of the two. The size of the caudal shield can scarcely therefore afford any safe inference with regard to the power of the animal to roll itself up. Since most of the members of this group are found in limestones, they appear, upon the whole, to be of less ancient date than the members of the previous group ; the oldest forms are those from the limestones of the lower Silurian system, as are also the genera Amjji/x, Asaphim, and lUcenus, taking them in their correct limits ; some peculiar species are also said to have been found in Tafel-schiefer. Calymene and Fhacops follow next, but the different species range through all the stages of the Silurian formation. Certain genera furnished with nine or ten body rings and a highly convex, axis, are, however, decidedly more modei'n, and seem to form the last link in the series of creation of these forms. With regard to the division of this very natural group into subordinate genera there appears to be one fact which has hitherto always been overlooked ; namely, the nature of the shell. I have already alluded to this, and have shown, when treating of general considerations, that many Trilobites which now appear to us to be smooth, were furnished during life with a peculiar granulated layer ; that others, on the other hand, had a peculiar sculpture and punctation in the shell itself, which is incompatible with the presence of a special upper membrane. Pursuing this idea, we discover that Trilobites with distinct granulations always possess a more than ten-jointed axis of the body, which in that case contracts very much posteriorly ; the Trilobites without granulation, on the other hand, never have more, and usually exhibit less than ten joints, of equal width in the body. Hence I believe myself justified in assuming that all Trilobites, furnished with an axis of ten joints which gradually becomes smaller towards the posterior part, possessed a granulated upper membrane, while those furnished with a fewer number of joints possessed a truly punctated or sculptured shell. There are, however, in both groups, genera in which the number of joints is ten. This difference becomes yet more marked when we consider that the Trilolsitcs not granvdated occur only in the most ancient and the newest Palfeozoic strata, while those, on the other hand, which are granulated, are found in the middle beds of that series. I have employed this structure as a permanent principle of classification,* and thus form two subdivisions of Trilobites having the power of rolling themselves up. * Dr. Beyrich lias questioned the value of this distinction, because in the genus Bronteus some species have a granulated, and others a lineated surface of the shell. But this genus belongs to the group of Trilobites not rolling themselves up, and does not therefore affect the question with regard to the other group in which we make use of the principle. A more important objection would appear to be, that certain species of Archegonus or PhilHpsia are granulated, and others lineated, since these genera do roll themselves up. It seems that in this genus, the last effort of a once numerous group, the character in question has degenerated into a mere specific distinction, although once distinctive of the main divisions of the genera, OF THE SPECIES. 79 Trilohifes having the poiccr of rolling t/icnwelves into a ball, with the axis of the body contracted posteriorh/, the shell (/ranulated, and generally more than ten body rings* Calymenid^E. This natural section I formerly subdivided according to the number of body rings into three genera, having respectively thirteen joints, eleven joints, and ten joints. There have since, howe\er, been found forms which render this method of grouping unadvisable, and I now prefer taking the course of the facial suture as the basis of arrangement. Trilobites capable of rolling themselves up, and whose facial suture terminates exactly in the angles of the cephalic shield. It appears that there arc but two genera that can be included in tiiis subdivision, and for these I retain the names of Calymene and Ilomalonotus. They are distinguished from one another by the cephalic shield, which in Calymene is furnished with a reflexed margin, over which the anterior extremity of the facial line extends ; whilst a flat expanded margin is found in Homalonotus, the anterior ends of the facial line meeting in the centre of the margin of the forehead, before the glabella. Other differences accompany this principal one, and justify the separation of the genera. Genus 11. — Calymene, Brongniart,f (Amphion and Zethus, Pander). Cephalic shield semilunate, rather strongly convex, furnished with a margin which is reflected all round, the largest and anterior division usually broken ofl'. The glabella, which is always rather contracted towards the anterior part, has a high, much reflected margin of articulation, and besides this always two or three sulcations at each side, by which it is divided into three or four lobes. If only two sulcations are present, then it is the anterior one which is wanting. The hindermost lobe of each side is the largest, and considerably arched ; the second from the posterior extremity is next in point of magnitude ; the third is usually the smallest, and frequently very imperfectly separated from the last or anterior one, especially in the most common species, C. Blumenbachii. The cheeks extend by the side of the glabella as independent convex plates, and bear strongly projecting but not very large eyes, the horny membrane of which is either wanting or pressed in. They are placed sometimes on the centre (C Blumenbachii), sometimes on the anterior half of * As additional characteristics, it may be stated that the members of tliis group ahvays exhibit a highly arched caudal axis, with distinct rings and radiated lateral furrows proceecUng from it. These furrows are absent, if not in both, at least iu the second group of the second division. The glabella likewise has (with only two exceptions) lateral fuiTows and lobes. t If Murcbison's figure of C. variolaris {Sil. Syst. PI. XIV, Fig. 1) be correct, the animal had thirteen body rings, and l)elongs to this division. Preceding authors, as Parkinson (Org. Rem. iii, PI. XVII, Fig. 16) and Brongniart {Cr.fos. PI. I, Fig. 3,) enumerate only eleven, indicating an affinity with Phacops. 80 SYSTEMATIC ARRANGEMENT the cheeks, and are in that case either more or less pushed inwards (C. Trisfnni) or outwards. The facial line projects forwards at the level of the eyes over the anterior margin of the head ; it is, however, connected at the side of the latter, which is turned under or anteriorly downwards by a diagonal suture running parallel with the margin itself, with its neighbour at the other side. From the point where both enter over the margin, they run almost parallel with each other towards the eye, form over it the covering plate, and turn from its posterior boundary in an S-shaped diagonal direction over the sides of the cheeks, continuing their course towards the posterior corner of the cephalic shield, which they divide exactly in its angle. The cheek-shield thereby assumes a narrow form, which is obtuse at the anterior, and pointed at the posterior part. The posterior angle of the cephalic shield is always obtuse, rounded, and not projecting. The thirteen body rings have a very convex axis, the separate members of which are very convex : they become gradually more narrow towards the posterior part. The lateral lobes are abruptly separated from the axis, are very convex, and their oblique impression is very strong, but short. The caudal shield is always narrower, but sometimes longer than the cephalic shield, and is embraced during the doubling-up process by the reflexed margin of the latter; it has a distinct, prominent, seven, nine, or eleven-jointed axis, Vv'hich is narrowed towards the posterior part, and rounded, and has the same number of lateral protuberances, or perhaps one less, which from the centre appear to be furcated. The free margin of the cephalic shield is only slightly enlarged. The upper side of the whole of the back was covered during life with a tolerably strong, unequally granulated, membrane, which in well preserved individuals can still be seen quite distinctly ; it is, however, more frequently absent. The granulation appears to have been most distinct on the cephalic shield, and on the axis of the body. Species are found in clayslate {Ccdymene Trisfani), in the very oldest limestones (C. poli/foma, Dalm.), and in the whole Silurian system to its uppermost strata. The most common species, C. BhimenbacJiii, has a very wide range, and is found in Europe, in South Africa, and North America. 1. C. Trist am : Limbo scuto cephalici antico valde reflexo, integro, oculis altissimis iuternis ; tuberculo capitis utrinque quadrilobato. Long. 3-3." Table II, Pigs. 7, 8. Bef. — Tristan, Jour», des. Mines, tom. xxiii, page 21. Brongn. Or. foss. 12. PI. I, Fig. 2, A-K. ScHLOTH. jYac/ifr. ii, 14. 2. 23. 2 and 40, Tab. XXII, Fig. 5. Dalm. Falcead 62. 3. Emmr. Dissert. 39. 4. Milne Edw. Crust, iii, 320. 5. Zethus verrucosus, Pander, Beitr. etc. 139, Tab. IV, C, Fig. 4, and Tab. V, Fig. 6. Cephalic shield strongly granulated when the shell is well preserved ; furnished with tubercles, or smooth ; the glabella contracted anteriorly, with an extremity which is rather straightly truncated and slightly curved : at each side there are three distinct furrows, which divide it into four almost equal lobes, becoming somewhat narrower towards the anterior part ; the lateral portions are very convex ; the eyes are placed close to the glabella, and affixed beside the second lobe ; the enlarged margin of the head is remarkably prominent, the centre of the anterior margin is erected or reflexed, the lateral lobes, on the OF THE SPECIES. 81 other h.and, are more strongly turned downwards ; wlien the animal is rolled up they embrace the caudal shield, so that the latter fits into tlie wide gap between tliem and the raised-up centre. The rings of the back are highly arched, but without peculiarities in other respects. Caudal shield oblong, triangular, the extremity prominent, and projecting considerably beyond the axis ; the latter seven-jointed, and furnished with an indistinct terminal joint ; the sides furnished with elevated, radial protuberances, which are furcated as far as beyond the centi'e. Locality. — The clayslate of Angers {Bed. Mus.), Nantes, the Cotentin. Found also at Valognes and Cherbourg ; in the transition limestone of Esthonia, near Revel, and Zarskoe Selo, also in boulders ( Collection at Halle) . Remarks. — 1. There is no doubt whatever that Zetfius verrucosus of Pander is identical with Cahjmene Tristam ; the structm-e of the glabella is quite the same. 2. The caudal shield represented by Schlotheim {ante cit.) probably belongs to this species. 2. C. Polytoma : Limbo scuti cephalici antico crenato ; tuberculo capitis antice latiori, in apice quadrilobato. Long. 2-3." Äp/.— Dalm. Palcead. 37, Tab. I, Fig. 1, a-c. Emmr. Bissert. 38. 2. Milne Edw. Crust, iii, 321. 6. L. v. Buch, Bcitr. 4.5. Asapkus Fischeri, Eichwald, Dissert. 52, § 58. Tab. Ill, Fig. 2, a. b. Calymene frmitiloba, Stschegloff. Amphion frontiloha, Pander. Beitr. 139, Tab. IV, Fig. 1 ; Tab. IV, B, Figs. 5, 6, 7 ; Tab. V, Figs. 3, ff, h, and 8. Cephalic shield less convex than in the preceding species, and the lateral lobes less turned downwards ; the glabella broader towards the anterior part, furnished with two lateral sulcations, dividing it into three lobes, that are broader anteriorly ; between the two anterior lobes there are three radiating furrows directed towards the centre of the head, which separate two smaller central lobes from the external ones. The enlarged border at the anterior margin is divided by eight furrows into nine rather acute notches or teeth, which very readily break oS", and are therefore wanting in many specimens. Eyes of a moderate size, placed in the line of the posterior lateral sulcation, projecting very far outwards, and inclosed by the indented facial line. Beneath them there seems to be another marginal concentric furrow. Body rings strongly arched, rather short. Caudal shield long, trilateral, rather acuminate ; the axis many-jointed (eleven-jointed according to Dalman's figure and Eichwald's enumeration), and reaches almost as far as the end ; the lateral folds probably not furcated (at least the figures indicate no such division). Loc. — The red transition limestone of East Gothland and Esthonia ; I have not myself seen a specimen. Remark. — The specimen represented by Dalman was deficient in the margin of the head, and so also was that figui-ed by Pander, Table V, B, Fig. 3. The presence of this notched margin, and the somewhat different structure of the glabella, scarcely justify the constitution of a peculiar genus, as suggested by Pander (who, however, seems to think his species different from Dalman's). His enumeration of the body rings (twenty in the body, four in the tail) is erroneous ; Eichwald had already enumerated them correctly. 3. C. Blumenhacliii : Limbo scuti cephalici antico integro ; tuberculo capitis subquadrilobo antico sive ultimo maxima, penultimo appeudiculato. Long. 1)4-3". Table II, Figs. 1-3. Bef. — Ch. Lyttelton, P/til. Trans, vol. xlvi, p. 598, PI. I, II. C. Moktimeh, II 82 SYSTEMATIC AKRANGEMEXT ibid 600. Em. Mendez da Costa, Phil. Trans, vol. xlviii, p. 286. I. ToRRUBiA, Jpp. P- L. Hist. N. Espan. pp. 83, 13, n. 96, Com. iii, n. 4. GuETTARD, Mem. de V Acad. Poy. des Sei. torn, xv, PI. IX (VII), Fig. 2. Wilkens, Stralsund Magas. i, 4, Tab. I, Figs. A-2. Klein, Sjwc. Descr. j)etrpf. Gedan. Tab. XV, Fio-s. 5-7. J. J. Walch, Text zu Knorrs Abbild, d. Fersfein, vol. iii, p. 222, Tab. IX, Figs. 1-5. Beckmann, Nov. Conim. Soc. Peg. Göttingen, torn, iii, pp. 101-2. Tril. fuberculatus. Brünnich, Nga. Sand. etc. i, 389. 1. Gehler, Progr. &r. 6. Fio-s. I-V. Blumenbach, Abbild. ?iaturk. Gegenst. i. Tab. L. Entom. paradoxus, Parkinson, Org. Bern, iii, PI. XVII, Figs. 11, 13, 14. Schlotheim, Petref. p. 39. 2. Wahlenberg, iV. A. f^«. viii, 31. 6. Ent. tuber culattis, Calymene Blumenbachii, Brongn. Or. foss. 11.1. PL I, Fig. 8, A-C. Schloth. Nachtr. ii, 13. 1. and 33. 1. Dalm. Palcead. 35. 1, Tab. I, Figs. 2. 3. a-c. Payton, Tril. of Dudley, Fig, 14. Cal. Blumenb. Green, Mon. 28. KLÖDEN.Fe/'sA d. Mark Brand. 105. Harlan, Med. and Pliys. Research. 300. Murchison, Silur. Syst. ii, 653. PI. VII, Figs. 5-7. BuCKLAND, Bridg. Tr. p. 46. Figs. 1-3. Bronn, Lethaa, i, 110. 99, Tab. IX, Fig. 3. Hisinger, Leth. Suec. 10, Tab. I, Figs. 3-4. Boeck, Gaea. Norw. i, 710. 16. Quenstedt, Weigmamis Archiv, 1835, i, 342. Emmr. Dissert. 39. 3. L. V. Buch, Beitr. z. Geog. Bussland, 47. Milne Edwards, Crust, iii, 318, 1. Cephalic shield lunate, the margin strongly reflexed but simple, thickened beneath ; o-labella indistinctly four-lobed, the first anterior lobe larger than the second, which is not so much separated from it as from the third ; the latter highly convex, but smaller than the fourth and posterior one. Eyes at the centre of the cheeks, not very prominent, placed on a line with the third lobe ; posterior margin of articulation much more narrow than the lobe preceding it. Thirteen rings in the body, which become successively smaller, without presenting any peculiarities. Caudal shield considerably smaller than the cephalic shield, the axis short, broad, seven-jointed, the two last joints indistinctly separated, the sides furnished with six radiating furrows, with intermediate ones along the whole length of the four central ones. The whole surface finely granulated in well-preserved fragments (var. pulchella, Dalman, /. c. Fig. 3), but more generally smooth, owing to the uppermost layer of the shell being absent. Remarks. — 1. I have compared all the authors quoted, as far as tliey were accessilile to me, and conv-inced myself that they all treat of this species. The figures of Brongniart marked A, B, and of Murchison, are the only ones sufficiently accurate ; in all the others the boundaries between tail and body cannot be recognized with sufficient distinctness. Dalman's figure with ten body rings is erroneous, and as erroneously copied by Hisinger. 2. Zet/ius verrucosus of Pander, which M. v. Buch considers as belonging to this species, I have preferred enumerating under Cal. Tristani ; his Z. uniplicatus (Beitrage z. Geogn. d. lluss. Reus. 138, Tab. V, Fig. 7), with which the representation of Razoumowsky (Ann. Sc. Nat. viii, PL XXVIII, Fig. 4) seems to correspond, has as little relation to this species. The glabella differs too much in both figures to permit of their being referred to Calymene Blumenbachii, even supposing it to have been imperfect iu the specimens that were examined by the authors cited. The species must therefore be regarded as distinct. 3. C. platijs, Green, Mon. 32, Milne Edw. Cr. I. c. 320. 4, I take to be a large specimen of C. Blumenbachii, with perfect granulations. 4. The numerous references above given sufficiently prove that this species is ^ddely extended ; it i.s, however, only found in limestones,* and if its relation in this respect in England can be assumed * Not so in England. — Editors. OF THE SPECIES. 83 as general, it belongs especially to the upper and middle Silurian strata {Ludlow, Dudley, IVenlock). In Sweden it is only found in the limestone of Gothland, which is wanting in Esthonia. In Germany it seems to occur in only travelled fragments, and appears to have been transported from the Scandi- navian mountains. Torrubia found it in Spain, on the frontier of Pardos, two leagues from Molina de Arragon. In North America it is found in difl'erent places, especially near Lebanon, in the state of Ohio, and at Trenton Falls, in New York. JSIurchison also mentions specimens from the Cedar Mountain at the Cape of Good Hope. 4. C. caHlcephata : Limbo scuti cephalici incrassato, oculis altis extemis, marginem superantibus ; tuberculo capitis utrinque trUobo : lobis posticum versus majoribus. Long. 2}i. Table II, Figs. 9-10. Be/. — Green, Mon. 30. Milne Edw. C'rmi. iii, 319. 2. More nearly allied to tlie preceding species in habit, but the cephalic shield is com- paratively shorter and broader, the sides more strongly curved, the posterior angles more turned backwards. The reflexed margin is not very strong, at least not at the anterior part, where it is usually highest. The eyes are rather small, but are remarkably prominent, so that they project from above over the external margin of the shield ; they are situated at the anterior part beside the front lobe of the glabella. This lobe is small and very narrow ; the second certainly less broad, but projecting more outwards ; the third is remarkably broad, large, semicircular, and separated for the greater part not only from the preceding lobe, but also from the axis of the head by a furrow (as in Cal. Trisfani). I have not seen the body and tail ; according to Green, the two together consist of fourteen rings, in which case only one would belong to the tail ; the axis of the latter is almost of equal breadth, therefore very obtuse at the posterior part, and the lateral lobes are not furcated. Loc. — Ixi North America, it occurs in Hampshire, Virginia; on the shores of the Miamis, at Cincinnati ; and in Indiana ; in a blackish gray limestone. This species is not found at Trenton Falls, where Cal. Blumeiihacliii is so frequent. I saw a plaster cast of the head (No 2, Green) in the Berlin Natural History Cabinet. Remarks. — The other species, considered as belonging to Calymene, are arranged by me under other groups. 1. Cal. bellahda. Dalm., and Cal. concMm«, Dalm., are the representatives of two particular genera; C. actinura. has been already mentioned (p. 69) and C. sclerops is a Phacops. Of C. punctata, I know only the caudal shield ; it forms according to Boeck (Gaea Norweg. 13) a particular genus, including also Cal. variolaris. 2. 1 can give the following explanations respecting Green's various species : oi C. selenecephala (p. 31 ; Milne Edw. 320, 3 ; Emmr. Diss. 40, fi) I have seen a plaster cast (No 3 of Green), but owing to the badly preserved state of the specimen from which it had been taken, I could not arrive at any sure specific characters. C. microps, Green (p. 34, Model 6), is a Phacops, and will be alluded to more particularly under this genus. C. anchiops (p. 35, Model 7) likewise belongs to the genus Phacops, but not C. diops, which forms a separate genus with Cal. concinna, Dalm. C. macrophthahna (p. 89) is a Phacops, and C. Bu/o (p. 41) likewise. C. odontocephala (Gr. Suppl. p. 9, Milne Edw. 322, 8) is likewise a Phacops, but a distinct species. 3. Murchison's Calym. Downinigice [Sil. Syst. ii, 655, PI. XIV, Fig 3) and Cal. tuberculata (A c. Fig. 4) belong to Phacops ; his Fig. 5, PI. XIV, is perhaps the caudal shield of a species of the latter genus, and in that case is identical with Ph. latifrons, to which C. tuberndata decidedly belongs.* 4. Milne Edwards's species (pp. 318-328) have been already explained, with the exception of Cal. Stokesii (p. 324, No. 13), (not Asaph. Stokesii of Älurchison — Sil. Syst. PI. XIV, Fig. 6), which is my Phacops latifrons. * The figure referred to represents the tail of a Proetiis. — Editors. 84 SYSTEMATIC ARRANGEMENT Genus 12. — Homalonotus, König, (Trimerus, Green, Murchison ; Dipleura, Green.) Cephalic shield hyperbolic, the anterior angle rather acute, the lateral margins gently arched, the posterior margin tolerably straight, without the angles being extended back- wards ; the whole nppcr surface gently arched, but the region at the external margin and the border at the posterior margin rather flatly expanded ; the latter separated by a furrow, slightly arched. The glabella undivided, broader towards the posterior than at the anterior part, and occupying about two thirds of the posterior margin. It then conti'acts a little, and assumes a round shape towards the anterior part ; without lateral lobes and sutures, but there is a trace of a furrow, which issued from the region where the e3'es are situated beside the glabella. This furrow is produced backwards towards the central line, and may sometimes be perceived with tolerable distinctness. Both furrows correspond with the posterior furrows of the glabella of the preceding genus, and separate the anterior cerebral region, the forehead, from the posterior or branchial region. Eyes placed near the centre of the glabella, just in the centre of the lateral parts of the shield, or a little behind it, depressed, corapai'atively smaller than in Cahjniene ; usually similarly excavated. Facial suture parallel anteriorly with the margin of the cephalic shield, but apart from the latter ; acutely angular, terminating on the flat extension of the cephalic shield ; thence turning in the form of an arch towards the eye, over which it forms the well-known covering plate, and then bends itself with an S-shaped curvature towards the posterior lateral angle, which is divided into two halves, either in the angle itself, or before the point towards the outer side. Axis of the body thirteen-jointed, decidedly narrower towards the posterior part ; the axis itself but slightly arched, owing to which the lateral lobes (the transverse diameter of which is smaller than the transverse diameter of the axis) are not as strongly separated from it as usual ; the posterior margin of each separate ring of the axis is produced forwards, acutely angular, sometimes (in Diplriira) even rather turned up ; the anterior or articular portion separated by a more or less impressed transverse furrow, proceeding from the posterior part of the ring. This character does not belong to any other genus of the Trilo- bites, and on that account appears to me a most important and peculiar one.* Caudal shield hyperbolic, longer, but much more narrow than the cephalic shield, and * In interpreting the fragments of tliis genus, we ought to be very particular in obserriug whether the impressions of the rings originate from the upper exposed surface of the back, or from the inner surface, which is turned towards the soft part of tlic animal. lu the former case the transverse ftirrow, which separates the articulating portion from the ring itself, appears as a fine line, and thus it has also been represented in Murchison's Figures (Tables VII and "N'lII, as far as Figs. 1, 2) ; in the latter it forms a deep broad furrow, which originates from a horny process of the ring that hangs downwards towards the inner part, and owing to this process being thick, it is also broadly and deeply impressed into the matter inclosing it. Thus appear Mm-chisou's Figures 3 and 4 in Table VII. Hence it follows that impressions differing from each other in the manner described do not indicate different species, but different sides of the shell of the same species. My Figures, Table IV, Figs. 10 and 11, show the difference in the rings of the shells of Homalonotus and Calymene more particularly, and respecting their significance I refer the reader to the explanations of the plates. OF THE SPECIES. 85 proportionalily smaller ; its axis has either no articulation at all, or a distinct one, very rapidly narrowed posteriorly and even at the commencement rather narrower than the last ring of the hody ; the external terminal angle more or less prominent. Remark. — The species of this genus are amongst the largest, but also the rarest Trilobites, and seem to be peculiar to the upper or central Silurian strata. I regret to say that I have only been able to examine casts or imperfect specimens. I recognized the granulation, however, iu botli most distinctly, where there were any remains of shell; the specimens deficient in shell, on the other hand, always appear quite smooth. According to the proportion of axis and lateral lobes, they furnish us with two subdirisions, which most authors enumerate as distinct genera. A. BipJeura, Green. — The outer end of the facial suture cuts in half the posterior angle itself. The joints of the axis are not broader than the lateral lobes, and very distinctly separated from the latter ; the latter have a process at the lower and outer extremity, with which they passed beneath the open margin of the cephalic shield during the rolling-up process. The posterior margin of each ring of the axis is strongly reflexed, and the ring in itself alone is highly arched. Caudal shield slightly pointed or produced forwards, the axis without joints, the sides even and ribless. 1, H. Decaji : Scuto capitis dilatato, dimidio latitudine vix longiori ; oculis ellipticis ; annulis trunci convexis, iu margine postico reflexo dilatatis. Long. 2K". Rpf. — B'qüeum Dekai/i, Green, Moh. 79, Figs. 8, 9. Bronn, Letluea, i, 1 13. 101 , Plate IX, Figs. 6, 7. Harlan, Med. and PJii/s. Research. 304. Emmr. i)m. 42, IV. RIiLNE Edw. Crust, iii, 316. Bronn, Leonh. and Br. Jahrbuch. 1840, pp. 447 et seq. Found in different parts of North America ; amongst other places at Lockport, Madison, Steuben, Cazenovia, Rochester, all situated in the state of New York ; also at Northumber- land, in Pennsylvania, and Mount Hope, in the vicinity of Baltimore. I have only had an opportunity of examining the two plaster casts (Nos. 30 and 31) of Green's fragments, and cannot therefore give an accurate description. The distinct granulation and the acute margins of the body rings render it certain that the calcareous shell remained in the actual specimens, which fact agrees very well with the absence of joints at the caudal axis. These joints are probably wanting only at the upper surface, and are visible on the inner surface, as is shown by the smooth individuals without a calcareous shell. Green's statement of there being fourteen rings is based upon an error, as the models have only thirteen ; for that which appears to be the first, is the thickened posterior margin of the cephalic shield. B. Trinierus. — The outer extremity of the facial suture meets the margin rather before the angle of the cephalic shield, externally. The joints of the axis are broader than the lateral lobes, very slightly separated from the latter, and not reflexed at the posterior margin; a distinct transverse furrow, which also continues over the anterior surface of the lateral lobes, divides the margin of articulation from the true ring. Caudal shield very prominent at the end, the axis distinctly jointed, the sides furnished with ribs. 86 SYSTEMATIC ARRANGEMENT j_ — Species without spines a)id tubercles. Trimerus, Green ; Homalonotus, König. 2. H. Knightii: Scuto caudie acuminato, annulis rhachis 8-9, costis lateralibus 6. Long. corp. 3-4". Re/.—Kö'üiG, Icones Sectil. i, 4, Plate VII, Fig. 85. Bronn, Letltaa. i, 119. 107, Table IX, Fig. 14. MuRCHis. Sil. Syst. n, 651, Plate VII, Figs. 1, 2. Milne Edw. Cr. iii, 315. Homalon. Z?<6?raOT5, Murch. ibid. Figs. 3, 4. Emmr. i)me?-;'. 41. 8. Bronn, Leonh. Jahrb. 1840, 445. Found in the grauwacke strata of the Eifel at Daun (according to specimens in Sack's collection), and in the upper Silurian strata of England. I have examined only two caudal shields of this species ; they are comparatively shorter and broader than that of the following species, the axis is more flatly arched, and more dis- tinctly pointed at the end, owing to a furrow which surrounds it. We can recognize in it seven distinct rings, besides the margin of articulation ; there is also an eighth, and indeed, even a ninth ring, but very slightly marked ; after which follows the short triangular pointed extremity. There are six strong broad ribs on the sides. The point of the shield is broken off in the specimen, but it must have been prominent. 3. H. delphinocephalus : Scuto caudse acuminate, in apice reflexo, annulis rliachis 11-12, costis lateralibus 8. Long. corp. 3-6". Bef. — Trim, delph. Green, Mon. 82, Fig. 1 (Model, No. 32). Emmr. Dissert. 41. 7. Bronn, Lethcea, i, 112. 100, Table IX, Fig. 5. Homalon. delphino-cephalus, Murch. Sil. Si/st. ii, 651, Plate VII, to Figs. 1, 2. Milne Edw. Crust, iii, 314. 1. Homalo. Ahrendi, RoMER. Verst. des Harzes, 39. 1, Tab. XI, Fig. 5. Found in a yellow grauwacke from the Eifel, containing a considerable quantity of iron (according to specimens in Sack's collection) ; also in the transition limestone of North America (Williams ville, Niagara, New York), and of England (Wenlock, Dudley). The rich collection of Mr. Sack contains perhaps a dozen caudal shields of different size (varying from half an inch to two inches in length), besides fragments of all parts of the head, and some joints of the body, all belonging to this species. They correspond in the principal points with Murchison's very accurate figure. The caudal shield, which appears to me to present the best specific character, is comparatively shorter, more acutely triangular, very prominently pointed at the end, and is here rather flatly extended. The axis is certainly more convex, but not so strictly defined as in the preceding species ; its rings are decidedly shorter but higher, and separately, with a much sharper edge. I have counted eleven distinct rings, and a very indistinct twelfth ring, besides the margin of articulation ; eight equally distinct ribs are perceptible on the sides, which are situated less towards the external part, and more posteriorly. OF THE SPECIES. 87 B. — Species with thick, si/mmetrical spines on the whole surface of the back. HoMALONOTus, Murcli. 4. H. armatus : Tuberculo capitis octies spinoso, lateribus scuti ceplialici bispinosis; annulis trunci bispinosis, rliachi caudse mutica. Long. corp. 3-6". Be/. — H. Greeiiii, Goldf. in Bronn n. Jahbr. 1843. 560. 5. Found in the grauwacke strata of the Eifel at Daun. The collection already alluded to contains some fragments of this species, from which I have constituted it, and which I shall now describe more particularly. It is comparatively broader than the other species, the cephalic shield is hyperbohc, slightly reflexed at the circumference ; the glabella is furnished with eight spines, namely, six larger ones in two rows, three on each side, and two smaller ones close to each other, in the centre before the two posterior ones. The cheek-shield has a large high spine at the sides, and rather behind the eyes ; besides this there is one spine at each side, on the elevated part of the posterior margin, and one on its centre. The body rings are each armed with two spines, one at each side, immediately before the front, where they become transformed into the lateral lobes. Caudal shield short and small, the axis six-jointed, unarmed ; each of the sides furnished with three ribs, of which the first bears a spine at each side ; the end of the sliield is oblong pointed, in the form of a spine. 5. H. HerscJielii : Annulis trunci quadrispinosis, lobis lateraliljus unispinosis ; rhachi caudse in basi 4 spinosa, lateribus miiticis. i?^/._MuRCHis. Sit. S?/sf. ii, 652, Plate VII, to Fig. 2. Milne Edw. Cri/st. iii, 315. Found in the upper Silurian strata of the Cedar Mountains, Cape of Good Hope, asso- ciated with Cat. Bliiment)acliii and C. TristaniQ:). According to Murchison's figure, the caudal axis of this species consists of fourteen joints, the two first bearing a spine at each side ; the sides seem to possess a number of ribs equal to the number of joints, but no spines. Of the body rings we find seven ; they appear to be furnished with four spines, two on each side, approximating to the lateral lobes ; and besides these there is probably another one on the lateral lobes themselves. The cephalic shield is wanting. B. Tritot)ites having the power of rolling themselves up, whose facial suture terminates in the external lateral margin of the cephalic shield. This section of Trilobites, originally established by Quenstedt, and confirmed by Emmerich, includes only the genus Phacops, and appears not to require the generic sub- divisions proposed by Milne Edwards and Goldfuss. 88 SYSTEMATIC ARRANGEMENT Genus 13. — Phacops, Emmerich. (Calymene, Audonim; Pleuracanthus, and Peltura, Milne Edw. ; Asaphus, Acaste, and Phacops, Goldfuss.) Cephalic shield semicircular, or somewhat parabolic (when the posterior angles strongly project) ; lunate ; acutely angular, or rather extended at the external margin, and thickened at the posterior margin ; the glabella highly convex, in some simple, in others divided into several lobes by lateral sections ; always broader at the anterior than at the posterior part, and at the latter, broader than, or as broad as the distance of both eyes from each other. The facial suture extends in a circle, concentric with the posterior margin, round the glabella, turns towards the eye, forms the covering plate, and then runs in an S- shaped curve from the posterior corner of the eye to the lateral margin, which it divides at a considerable distance in advance of the posterior angle. Eyes remarkably large, very prominent, forming a segment of a cone, and having large semicircular lenses in considerable but varied number. Posterior angles of the cephalic shield either obtuse, or longitudinally extended. Body rings always eleven, the axis rather smaller than the lateral lobes, both separately convex, the extremities of the latter either rounded off, or pointed in the shape of a spine ; the joints of the axis distinctly contracted towards the posterior part. Caudal shield partly obtuse, partly acute, parabolic, the axis distinctly jointed ; the sides strongly ribbed. The upper surface in all well-preserved individuals is granulated, but is smooth in those which have lost their natural shell ; the body rings also are frequently smoothed by friction, even when the shell is present. Group A. — Species with a simple, undivided, trapezoidal glabella, which at the poste- rior part is provided with a short peduncle, and has beside it two small tubercles. Angles of the head obtuse, the caudal shield rounded at the end. 1. Ph. latifrons : Lateribus tubercvili capitis rectis ; rhachi caudse 7-9 annulata, costis lateribiis 5-7. Long. 1-3". Table II, Figs. 4-6. fief. — Cali/mcnc macrojilithalma, Brongn. Crust, fuss. PI. I, Fig. 5, A-C. Schloth. Petref. Nachtr. ii, 15. 34. KNORRandWALCH, Natur(/cschichte der Verstein. Suppl. Table I, Figs. 4, 5. Zeno, Neue Phi/s. Bell. Table I, Fig. 2. Honinghaus, Noggsreautli s Bheinb. und Weslph. 291, with figures. The same author, in the Isis, 1824, pp. 464, 534, 986; Table V, Figs. 1, 4. and 1830. 95. Table I, Fig. 2, a. c. Count Sternberg, Fer/i. d. Vnterl. Mus. 1825. 75. I, Table I, Fig. 1, A, D. Dalm. Palcead. 63. 8. Bronn, Leih. i. 111. 2, Table IX, Fig. 4, a. b. Green, Mon. of Trilob. 39. Murchison, Sil. Si/st. ii, 655, PI. XIV, Fig. 2. Buckl. Bridff. Tr. PI. XLVI, Fig. 4. Emmerich, Dissert. 19. 1. Cal. latifrons and SMothemii,^ViO'&-(i,Leonh. Zeit sehr, f d. Miner. 1825. 317, Table II, Figs. 1-8., Dalm. Palcead. 64. 10. 11. Römer, Rhein. 81. 68. Cal. bufo, Green, Mon. of OF THE SPECIES. 89 Tril. 41. Milne Edwards, Cmsl. iii. 327. 19. CaJ. taherculata, Murch.ü. 65G, PI. 14, Fig. 4. Milne Edw. Crust, iii, 325. 14. Portlock, Bei). 284, PI. II, Fig. 10. Cal. (jramdaia. Count v. Münster, Beiir. iii, 36. 3, Tab. V, Fig. 3, a-d, and Cal. Icems, ibid. Fig. 4. Cal. Stokesn, Milne Edw. Crust, iii, 324. 13 Trinucleus {.^) leevis, Coxs-!!ii: v. Münster, i?«7/-«y(', N. 116. 1, Tab. X, Fig. 6. (?) Cal. Jordani, Romer, Verst d. Harz. 37. 1. PI. XI, Fig. 4. Loc. — The transition limestone of the Eifel, the Hartz, the Fichtelgebirge, Bohemia, England, and North America. This common Trilobite is rarely well and perfectly preserved, hence the many designa- tions that have been given to it. Perfect specimens with the shell are always strongly granulated, as I have represented it. The granulation is most distinct on the glabella and on the eyelids less so on the body-rings, and slighter everywhere on the sides, where indeed it is usually altogether wanting. It is likewise not seen when the true shell is absent. Brongniart, Bronn, and Murchison have figured such individuals as the normal state. The axis of the tail, in specimens without a shell, has only seven rings and five ribs ; two more rings and ribs are seen when the shell is present, but the two latter are very slightly marked, and sometimes can scarcely be recognized. The eye, according to an accurate calculation, has from 99 to i 04 lenses, many of which are frequently wanting in the centre at the upper margin in some individuals, but are present in others. There are five lenses at the anterior part, and two at the posterior, in the first row ; the rows then increase at each side by from one to five lenses in the vertical row, upon which rows of six and seven lenses alternate several times with one another ; there are usually from sixteen to eighteen of such rows forming each eye. Remarks. — 1. Brongniart described as Cal. macrophthahna a species quite different from this, ^-ith a glabella divided in lobes ; and not only has the present species, but also the C. iiiacrophthalma of later authors, been described as belonging to various individuals resembling his species. The latter, however, is much more common than the former or Brongniart's, and has been almost always mistaken for it, although totally distinct. Honinghaus and the natm'alists of Bonn seem afterwards to have repeated the error committed by Brongniart himself, and Count Stei'nberg followed in their footsteps. Bronn, who at first correctly considered his Cal. Schlotheimii and C. latifrons as different, subsequently returned to the error of his predecessors. Murchison and Emmerich recognized the difference of fig. 5 and fig. 4 of Brongniart's representation, but suffered the name erroneously given by Brongniart to remain, as referring to the really undescribed figure marked 5. Milne Edwards was the first who announced Brongniart's error [Crust, iii, 323, note 2), and who restored its original name to C. macronh- tlialma, although the introduction of a new name for the second species was superfluous, since it had already received two from Bronn. I therefore i-etain the name originally given by this careful in- vestigator. 2. In the first and second chapter, I have mentioned the species here described as /-"/;. latifrons under the name of Phacops maci-oplitlialmiis, not choosing to difi'cr from the prevailing custom, and I therefore called the species as it had hitherto usually been called. This, however, must not be done for the future. 2. Ph. protuberans : Lateribus tuberculi capitis subangulatis sive arcuatis ; oculis miuutis, externis. Long. 2". Table III, Fig. 6. Ar/.— Emmr. Dissert. 19. 2. Sternb. T'er/i. d. Valerl. 31us. 1825. 77, Tab. I, Fig. 2, a. c. Cal. proluh. Dalm. Pahead. 63. 9. Loc. — A gray limestone of the Branikberg, near Prague, (Nos 2, 18 of the Berlin Museum). It is said bv Count Sternberg to occur also in Westphalia. 12 90 SYSTEMATIC AREANGE^iIENT This species approximates very nearly to the preceding, but can be readily distinguished from it. The glabella, which in other respects is similar, is not quite so broad at the anterior part as in Ph. lafifrons, and its sides are rather angular, or at least bent in this, but extend in quite a straight line in the former ; the eyes, which are small, are situated beside the anterior part of the angle, close to the margin of the head, and have only few lenses (from two to three rows) ; the circumference of the cephalic shield is more broadly reflexed, and does not present quite so acute an edge ; the posterior margin seems to be less produced The body and caudal shield are not yet known ; the individual which I examined was without a shell, and therefore quite smooth. Group B. Species with a glabella divided into lobes ; the isolated little tubercles on the posterior angles are wanting, and instead of them there is a transverse protuberance. Remark. — The glabella in this group has always three lateral lobes between the large trapezoidal front lobes and the posterior margin of articulation, therefore four lobes in all (including the anterior and chief protuberance). Of these the third is sometimes very small, and on that account appears occasionally to have been overlooked. Sub-Groiijj {a). The posterior extremity of the caudal shield rounded or obtuse.* 3. Ph. anchiops : Tuberculo capitis elevato, lobis lateralibus obsoletis (s. mutilatis); oculis maximis; rhachi caudse 12 anuulata, costis decern. Long. 2-4". Bef. — Calt/m. ff«r/<. Green, J/o». o/ yn7o(5. 3.5, Mod. 7. Emmr. Z)m«-^. 22. 8. Milne Edw. Or. iii, ,325, 15. Var. minor. Asajjh. Wetlimlli, Green, Mod. 20. Locality. — In a black limestone of North America, at Ulster and Murron (New York). The plaster cast which I examined, and which is in the Berlin Museum, reminds one of the preceding species, and the present is principally distinguished by a longer urn-shaped glabella, sulcated posteriorly, in which, however, I could not perceive any distinct lateral lobes, with an acute outline as usual. On the other hand, there is only an im])erfect lobe, which is isolated, and projects near the tubercle of the eye at the glabella ; and instead of the peduncle, I notice before the margin of articulation a short transverse prominence scarcely disconnected. The original from which the cast had been taken was, however, evidently impei-fect. The body has distinctly eleven joints ; there are twelve joints of the caudal shield, and ten lateral ribs towards the posterior part, but rather indistinct. Green, owing to this, enumerates only twenty rings in all, which would leave nine for the tail. Remark. — Asaph. Wetherilli, of which I examined a plaster cast at Berlin, appeared to me to be a smaller individual of the species described by Green as Cal. anchiops. The head is, however, so in- distinct, that accurate determination is impossible ; I was able to recognize the eleven body joints with certaintv. * From observations which I have made on Phacops sclerops and P. procerus, and which I shall subsequently make known more in detail, I believe myself justified in inferring that elongated pointed angles at the cephalic shield existed in most of the species of Phacops liaAnng a lobed glabella, but were broken off with the calcareous shell. These species therefore can no longer be grouped according to the form of the cephalic shield. OF THE SPECIES. 91 4. Ph. srierops : Protubcriuitiie frontalis lobo antico maximo rcnlfoniii, lobo quarto minuto, rcliquis abrupte augustiori ; rliachi cauthe H aiuuilata, costis latcralibus sex. Long. 114-2." Table IV, Figs. 5-6. R(f. — Ca/j/m. sclerops, Dalm. Palcead, 39. 5. Milne Edw. Crust, iii, 322. 9. Phac. sderops, Emmr. Dmert. 22. 8. Pander, Beitr. 138, Tab. XLVIII, Fig. 9, Tab. V, Fig. 4, Tab. VI, Fig. 10. Zoc.— Swedish limestone at Husbj'fjol, in East Gothland; in gray limestone near Skarpasen ; in red limestone near Furudal ; in Dalecarlia in red limestone. This distinct species can readily be known by the peculiar form of its glabella, which consists of five lobes, of which the anterior and largest is singularly wide, and projects laterally over the eyes ; the second is narrower and posteriorly smaller, the eye corresponds with it ; the third is a very small narrow lobe, and the fourth has pretty much the same size as the margin of articulation following it. The eyes are large and prominent, the facial suture is distinct (Dalman was the first who described the facial suture in this species as terminating in the lateral margin) ; the posterior cephalic angles are obtuse. The axis of the tail consists of four distinct, and four rather more indistinct rings, and has from six to seven lateral ribs ; its extremity is obtuse, and so also is the front of the cephalic shield. Remark. — From examining a great number of specimens, I have had an opportunity of convincing myself that this species does possess long projecting angles at the cephalic shield, and thereby approxi- mates so near to Ph. conophthalmus of Boeck, that I am inclined to doubt their specific distinctness. 5. Pli. cunuphtliulinus : Protuberantia frontali antice latissima, posticum versus valde coarctata ; oculis minutis ; rhachi caudae 7 annulata, costis laterahbus 9. Long. 2K". Ref. — Emmr. Dissert. 21.7. Boeck, Gaea Norm, i, 4. Loc. — The yellowish gray limestone of Revel, and Ladegaards Oen at Cliristiania ; found likewise in boulders at Gussow, in Mecklenburg (Berlin Museum). This singular species resembles the preceding one in the formation of the glabella, but is readily distinguished by the pointed angles of the cephalic shield. The anterior large lobe of the glabella has an oblique rhombic form with rounded angles ; the second is obtusely trilateral, rather truncated towards the posterior part ; the third is the smallest, and is rather narrower than the margin of articulation which follows it. The eyes, which are not large, correspond merely to the second lobe of the head. The facial suture is very distinct. The cephalic shield, which is very broad at the sides and rounded off at the anterior part, is rendered conspicuous by a sharp point at the posterior extremity, which point is about as long as the four first body rings ; the caudal shield has a ten- jointed rounded axis, obtuse at the posterior part, and nine diagonally-furrowed latei-al ribs ; it is much smaller than the cephalic shield, and not pointed at the end, but perceptibly incurved. When rolled up, this incurvation is closely embraced by the under margin of the cephalic shield. Remarks — 1 . The cephalic shield from the transition limestone of llevel, figured by ScLlotheim in Leonhard's Taschenbuch, 1810, Table I, Fig. 6, I consider as most decidedly belonging to this species. .2. Cahjmene microps (Green, Mon. p. 34; Milne Edw. Crust, iii, 326. 17) is very nearly allied to the species just described, and may perliajjs be the same. 92 SYSTEMATIC ARRANGEMENT 6. Ph. odontocephalus ; Protuberantia frontali antice ovata, lobo sccuudo coustricto ; limbo ante protuberantiam octies dentato. Table IV, Fig. 4. Ee/. — Calym. odontocephala, Gkeen, Sill. Am. Jourii. vol. xxv, p. 334. Harlan, Med. and Pliys. Res. 30 1 . Loc. — In a gray sandstone at Ulster, New York, U. S. I saw the plaster cast of a cephalic shield of this species at Berlin. The glabella is short at its anterior extremity, ovate, moderately convex ; the second lobe is reniform, almost isolated, only connected with the central axis by a short peduncle ; the third is a narrow transverse protuberance, behind which there follows a fourth broader one, perfectly resembling the margin of articulation. The large eyes correspond with the kidney-shaped prominence ; they reach neither to its anterior nor to its posterior extremity, and are far removed from the external margin. A broad flat border encircles the latter, in which may be distinguished anteriorly, and placed in front of the glabella, eight obtuse indentations, inclosed by an impressed furrow (? of the facial suture). The posterior angles of the specimen were indistinct, but appeared to be obtuse ; body and caudal shield are wanting. Sub-group (i.) The extremity of the pygidium sharply angulated. 7. Ph. macrophthahnus ; Lobo autico capitis acutangulo, lobis sequentibus sequalibus ; rliaclii caudse 10-12 articulata, scuto in apice acuminato. Long. 1-1J4". Bef. — Cahjmene macr. Brongn. Crust, foss. 14, PI. I, Fig. 4, A, B. Milne Edw. Crust. iii, 323. Pander, Beitr. 138, Tab. IV, B, Fig. 8 ; Tab. V, Fig. 5 ; Tab. VI, Fig. 9. C. Bowningi(B, Murchison, Ä7. Sgst. ii, 655, PI. XIV, Fig. 3. Buckl. Bridg. Tr. PI. XLVI, Fig. 5. Milne Edwards, Crust, iii, 324. 12. Loc. — The older transition limestone of Huraandiere in Brittany, and in the Petersburg hüls. This species approaches very near to C. sderops in point of habit, but is much more slender ; the glabella is similarly four-lobed, and the eyes are much larger, almost as large as in Ph. rotundifrons. The anterior lobe of the glabella is obliquely rhombic, rather acutely angular at the anterior part ; the three following lobes between it and the margin of articulation become successively rather smaller, and the posterior lobe is the most strongly arched among them. The prominent eyes reach from the anterior margin of the cephalic shield to the posterior. The caudal shield, according to Pander, has from ten to twelve joints in the axis, slight lateral ribs, and a sliort but acute termination. 8. Ph. rntundifrons : Tuberculo capitis antico ovato, lobis sccuiulis triangularibus, tertiis minutis spii-ajformibus ; oculis maximis ; rhacbi caudali 7-8 anuulata, costis lateralibus sex. Long. 2". Table IV, Pig. 2. Bef. — Emmr. Dissert. 23. 10, c, Fig. Pleur. laciiiiatus, Romer, d. Blieiu. Uebergmigstel 83. 69. 2, Tab. II, Fig. 8 Loc. — Described from an impression in plaster in the Museum at Berlin ; tlie original was found at the Kalauerberg (in the Dietzhatze, in the Westerwald near Dillenburg). Exactly similar to the preceding species in its entire habit ; but the anterior large lobe of the glabella rather more oblong and of a short egg-shaped form ; the second has the OF THE SPECIES. 93 form of a triangular lobe ; the third of a narrow transverse protuberance, the margin of articulation exceeding it in point of width. The eyes are enormously large, and occupy the entire sides of the cephalic shield from the anterior to the posterior margin. There are eleven body rings. Caudal shield oblong, trilateral, rather narrow, the axis furnished with seven distinct rings, the sides with six short ribs, and the extremity acutely angular. Remark. — According to the researches of Römer {d. Rhein, uhergamjsgel , 83. G9. 2), this species possesses not merely elongated cephalic angles, but also dentations to the caudal shield, and belongs therefore to the last group, called by Milne Edwards Pleur acanthus. I have therefore indicated tlie ceph.alic angles and caudal points according to Romei-'s drawing in the former figure, which represented mere impressions in stone. Römer calls it Pleur. laciniatus. 9. Ph. proeevtts : Tuberculo capitis antico rhombeo, secundo et tertio sensim minoribus, hoc a spire articulatoria, longius distante ; rhachi caudali 8 annulata, costis lateralibus septem. Long. 2". Table IV, Fig. 3. Be/.—EuMR. Dissert. 25. 14. Loc. — The Bohemian grauwacke of Ginec. Comparatively shorter and broader than the preceding species ; the anterior lobe of the glabella forming a highly convex, granulated, oblique, rhombic plate, to which the second wedge-shaped lobe is as closely joined as the third and narrower one, which is contracted laterally, is to this. The margin of articulation then follows posteriorly at a somewhat greater distance. The eyes not large in proportion. They correspond entirely to the second lobe of the head, beyond which they do not project at all anteriorly, and but little posteriorly. I have not seen the body. The caudal shield is trilateral, heart-shaped, convex, pointed at the end, and has eight rings, successively becoming narrower, besides an ovate terminating joint ; seven broad ribs, rather impressed longitudinally, are visible on the sides. The smaller anterior margin of articulation has been left out in this calculation ; if we count it likewise, it would increase the number of rings, including the terminal joint, to ten. Remark.- — I have recently had opportunities of examining many specimens from the ^Mineralo- gical ^Museum of the University of Halle. In many of them there are distinct traces of long processes on the cephalic shield, and of a spine at the extremity of the caudal shield, which suggests the idea that Phacops proavus may perhaps be identical with Ph. mucronatus. Siih-(/roup (c). The caudal shield is pointed at the extremity, and has no lateral spines. 10. Ph. Hausmanni : Oculis maximis, usque ad limbum scuti cephulici cxtensis ; rhachi candie 19-20 annulata, costis latei'alibus 15. Long. 3-5". Re/. — Jsaj)/i. Hausmaimi, Broügü. Cr. Joss. 21. 3, PI. II, Fig. 3, A, B. Schloth. Naclitr. ii,20. 35, Tab. XXII, Fig. 7. Sternb. VerhancU. 1825, 77, Tab. II, Fig. 3, A-C. Dalm. Palcead. GG. 4. Phac. Hausmanni, Emmr. Dissert. 24. 13. Loc. — The gray transition limestone of Bohemia, on the left shore of the Beraun, near Karlstein, and at the shores of the Moldau, near Kosorz and Brauik. The largest species of the genus, and particularly distinguished by its very large eyes, the lenses of which, however, are remarkably small. The glabella is shorter and broader 94 SYSTEMATIC ARRANGEMENT than in the other species of this group ; the three central lobes are nearly of an equal size, and the eye reaches not only beyond the second, but even beyond the fourth, and almost as far as the broad flat margin. The posterior angle is moderately pointed, probably as long as four or five articulations. The large trilateral caudal shield has an a.xis of from nineteen to twenty-two joints, and from fourteen to fifteen lateral ribs. It is, however, moderately convex, and extended in a flat border at the circumference, which forms a carinated angle, |)ointed at the extremity. The surface is finely granulated wherever the shell is preserved, but smooth when it is absent ; the lateral ribs, in the latter case,do not appear to be grooved, but merely flattened, but they have a double granulated I'idge. of unequal height, when the shell is present. Remarks. 1. Brongniart, who knew this species b}' fragments only, represented the caudal shield as beino- rounded at the posterior part, which probably may be in consequence of the defective state of his specimen. I therefore do not consider this caudal shield different from that represented by Sternberg and Schlotheim, as Milne Edwards supposes (see p. 312 of his work). 2. The angles of the cephalic shield are wanting in Count Sternberg's figure ; they are, however, present in the perfect specimens which I saw at Berlin. A well-preserved head is very rare. 3. Asaph, auriculatus, Dalm. [Paltead. 6. 6. 3), which is based upon Count Sternberg's unknown individual (see his work, p. 80, Table II, Fig. 2), is beyond a doubt a smaller, younger specimen of Ph. Haii.mumni, and therefore cannot be admitted as a species. 11. Ph. caudatti.'s : Ocuhs miuorihus, nee anticum nee posticum limbum scuti cephalici attiugen- tibus ; rhachi cauda; 14 annulata, costis lateralibus octo, limbo in apice acuminato. Long. 2-3". Uef.—Triloh. caudat. Brunn, Kjob. Scllsk. Skrift. N. S. i, 392. 3. Parkinson, 0/y. Bern. PL XVII, Fig. 7. Schloth. Nachtr. 35. 11 (or 21. 4). Asaph, ccmd. Brongn. Crust, foss. 22. 4, PI. II, Fig. 4, a-c ; PI. Ill, Fig. 9. Dalm. Palcead. 42. 2, and 65. 2, Tab. II, Fig. 4. Green, Mon. of TrU. 50. Buckl. Bridg. Tr. PL XLV, Figs. 9-11, and PL XLVI, Figs. 11, 12. Murchis. Sil. Sj/sf. ii, 654, PL VII, Fig. 8, a. Asajih. tuberoilato-caudatim, Murchis. Sil. Si/st. ii, 654, PL VII, Fig. 8, b. Milne Edw. Crust, iii, 308. 2 (specimens with the granulation well preserved). l,oc. In a gray limestone in England (Dudley, Ludlow), in Sweden (Gothland), and in North America (Lockport). This species is nearly allied to the following one, but has characteristic distinctions ; the anterior tubercle of the head is very large, and laterally very much produced forwards, by which the eyes are thrown back; the latter are smaller than in P. Ilausmanni. They do not reach beyond the anterior margin of the second lobe of the head, and only just reach the front at the posterior part ; the posterior angles of the cephalic shield reach to the centre of the body rings, the latter are gradually more pointed towards the posterior part. The caudal shield has an axis with about fourteen joints, which is distinctly rounded at the posterior part, and does not pass into the spine at the extremity ; there are eight ribs on the sides, each divided by a diagonal furrow ; the broad expanded margin is lengthened into a moderately long point at the posterior part, which is usually nearly as long as one half the length of the axis. OF THE SPECIES. 95 13. Ph. nmcronatus : Oculis mediis, lobo capitis sccundo ct tcrtio aiquantibus, caudic iliaclii 10-1 1 articulata, costis hiteralibus 8-9, scuti apice mucronato. Long. 8-4". Ecf. — Asaph. )Hncro)iatu-re.vochus. 3. Cahjmene bellatula, Dalm. {Paheud. 3G. 2, Tab. I, Fig. 4, Rising. Leth. Stiec. ii. Tab, I, Fig. 5, Milne Edwards, Ciiist. iii, 321. 7, Emmr. Dissert. 31. 8), likewise does not belong to my genus Cyphaspis, as I formerly supposed, judging from a damaged specimen, but must be referred to a peculiar genus which Dr Löven {ante, p. 1 10) calls Cyhele, and in which he also includes the Calym. verrucosa, Dalm. {Arsber, etc. 1827. 52), together with Trilob. velutus, Schloth. {Petref. supplement ii, 40, Tab. XXII, Fig. 5), found at Revel. I must refer to Dr. Löven's treatise for the characters of this new genus, which has been very thoroughly described by him.* Genxs 15. — Proetus, Steiningcr, (^Eonia, Burmcister; Gerastos, Goldfuss.) Cephalic shield semicircular, surrounded by a thickened margin ; the posterior angles do not project perceptibly; the glabella is very convex, parabolic, rounded at the anterior part, undivided, without any lateral lobes ; at the posterior part it is as broad as the margin, to which it is immediately joined. The facial suture projects over the anterior cephalic margin on a line with the eyes, is thence directed towards the eye, forms the covering plate, and runs at first straight, afterwards in an S- shaped curve, to the posterior margin, which it penetrates beyond the centre, in an oblique direction towards the external part. Eyes of moderate size, very prominent, smooth, joined rather closely to the glabella. Body axis ten-jointed, the joints gradually more narrow towards the posterior part, strongly arched, abruptly separated from the lateral lobes by a peculiar furrow, these lobes having an oblique indentation. Caudal shield corresponding with the cephalic, but smaller, the axis highly arched, short, distinctly articulated, the sides furnished with slight furrows or obsolete ribs, the margin even, but having a very acute angle. The surface of the shell almost smooth, but with distinct traces of granulation on the glabella, and on the cheeks beneath the eye. Remark. — Prof. Goldfuss described species of this genus under the name of Gerastos, but con- nected with them, as I also did, other Trilobites which do not belong to the group. Mistakes of this kind would have happened less frequently, if former authors had furnished us with as distinct illustrations as we have at present in my Monograph, and in the works of Goldfuss, Löven, Beyrich, and others. P. Cuvieri : Protuberantia verticis latissima, longitudine vix angvistiori, obsoletissime granulata ; angulis scuti cephalici obtusis. Long. 1". Tab. Ill, Figs. 1, 2. * The following are the characters given by Professor Löven for his genus Cyhele : — Caput breve latum. Scutum centrale sublunatum, latum. Sutura pone oculum subrecta, ad angulum ducta. Oculi minuti arcu infraorbitali elevato, angusto. Thorax articulis (in una specie) duodccira. Terga convexa. Pleuraa sulco longitudinal! in partem anticam dins» syndesmalem breviorem, et posticam, magis minusve productam. Pygidium thoraci ex parte conforme, minutum, ex articulis numerosis coalitis, quorum basales aliquot majores, pleuris prrediti, reliquis in caudam lauceolatam arctius connatis. Oversii/t af Kongl. Vetenskap. Arnd. Fork. 1815, No 4, p. 110. — EniTORS. 100 SYSTEMATIC ARRANGEMENT Jlpf- Steininger, Bemerk, ii. d. Vorst. d. Eifel. Trier, 1831. 4, No. 52. 3Iem. de la Soc. Geol. de France, i, 359, No. 52, PI. XXI, Fig. 6 (1834). Gerastos hevif^afns, GoLDF. Leonh. and Bronn. n. Jahrb. 1843. 557, Table IV, Fig. 3. Locality. — A yellowish-gray limestone of the Eifel, near Blankcnheim, according to specimens in Sack's and the Academy collections. Glabella not very convex, without distinct granulation ; it does not reach the anterior maro-in, which is reflexed : eyes rather behind the centre, surrounded externally by an indented I'ing, the cheeks beneath them distinctly granulated, their angles rounded. Body rings not remarkal^le ; the caudal shield rather small, and flat like the axis, the latter nearly eight-jointed, but the last joints indistinctly separated ; the sides furnished with six, more or less deeply-marked, furrows. Remarks. 1 . The Trilobite above described I formerly considered to belong to Calymene conchma, Dalm. iPalmad. 40. 7, Tab. I, Fig. 5 ; Milne Edw. Crust, iii, 325. 16 ; Asap/i. cone. Emmr. Dissert. 35 19). Dr. Löven, however, has since published a very accurate description of Dalman's species (49 Tab. I, Fig. 2), and proved that it is not identical with Proetus Cuvieri. But he is of opinion that both Trilobites belong to the same genus, which I cannot admit. I prefer separating Dalman's species from the species of Steininger, giving the new genus my former designation of Jeoiiiu, and distinguishing it from Proetus by the following characters : Glabella (which is shaped like a violin) has at each side three slight furrows, is contracted behind in a pedunculated stape, and furnished with two little tubercles close to the peduncle. The angles of the cephalic shield terminate in long spines. The eyes are oblong, lunate, and flatter than in the other. The axis of the body is comparatively narrower, but likewise ten-jointed. The caudal shield is not so obtuse, its axis longer and narrower, and its sides have deeper radi- ations. The following species belong to this new genus : 1. Ae. concinna [Proetus concinnus, Löven 1, 1; Calymene cone. Dalm.). The cephalic shield I have copied from Löven's figiu-e. Tab. V, Fig. 8. 2. Ae. Stokesii [Asap/i. Stokesii, Murch. Sil. Syst. ii, 625, PL XI Y, Fig. 6; Löven 50, Tab. I, Fio-. 3). From the figure by Löven I have copied the cephalic shield. Tab. V, Fig. 5. 3. Ae. verticuUs, Mihi, Tab. V, Fig. 9 (Gerastos cormitvs, Goldf. 558. 3, Tab. Y, Fig. 1). This species is nearly related to the former, and perhaps identical. I have formerly described it from an imperfect specimen as Trilobites verticalis, and therefore did not recognize it properly ; the present fio-ure is more correct. The glabella is flat and fiddle-shaped, becomes gradually narrower towards the anterior part, and exhibits at each side three oblique sulcations, of which the posterior rans in a curve towards the posterior margin, nearly reaching it. Traces of granulation may be seen on its summit. The oblong, lunate eyes correspond to the two posterior cephalic lobes ; they are externally surrounded at their base by a furrow. The margins of the cephalic shield form a protuberance, which passes over at the angle into the long powerful spine, but is sulcated at the upper part. The body joints are short but rather broad, uarrower, however, than the lateral lobes. The caudal shield is rather less than a semicircle, its axis acutely pointed, seven-jointed ; the sides have five flat elevated ribs, their extremities gradually becoming broader and indented by an additional radiated furrow. Occurs in the Eifel near Bensberg (Sack's collection). 2. Calymene diops, Green [Mon. 37, Fig. 2 ; MontJily Amcr. Journ. of Geol. 559, Tab. XXII, Fig 2; Milne Edwards, Crust, iii, 323. 10; Harl. Med. and Plnjs. Res. 301). The figure, Tab III, Fi^. 5, is copied from the specimen in plaster of Paris of the Berl. Museum ; this species seems rather to belong to the new genus Aeonia than to Proetus, and I shall therefore not attempt a further description of it until I have accurately examined original specimens. The figure is sufiSciently recognizable. 3. Gerastos granulosus, Goldf. (558. 2, Tab. V, Fig. 4), belongs decidedly to Proetus. It is distinguished from Pr. Cuvieri by its more elongated and more strongly granulated glabella, and by the more pointed angles of the cephalic shield. OF THE SPECIES. 101 GeiiKs 16. — Archegonus, (Phillipsia and Griffitiiidrs, Portl.) The cephalic shield is rather large, parabolic, moderately convex, with a niarcrin but slightly thickened, the glabella is evident, but not so distinct as in the former genera, its form is different, its sections and lobes not very depressed. The postci-ior angles of the cephalic shield are either pointed or obtuse. The facial suture commences at the anterior margin of the cci)halic shield, turns thence somewhat inwards towards the eye, forms the covering plate, and extends in a curve to the posterior margin, which it intersects near the middle. The eyes are small, particularly low, but frequently long, lunate, and of a finely trans- parent lattice-work. The axis of the body consists of nine short, highly arched rings, and is only very slightly narrowed towards the posterior part ; the lateral lobes are as broad as the axis, and have only a distinct oblique furrow. The caudal shield is but very little smaller than the cephalic, its form parabolic ; it is highly arched at the axis, and less so at the sides ; the axis is distinctly articulated, and consists of twelve or more joints ; the sides are furnished with radiated furrows. The surface of the shell is granulated in most of the species, but in some it is finely lineated. Localifi/. — The carboniferous limestone and other contemporaneous beds. Remark. — WLeu I first described this genus (which I did contemporaneously with Portlock), I knew accurately only one species, and owing to the shell of this species possessing a lineated surface, I placed Archegonus in the next group of Trilohites. This genus, however, has become better known since, and it has been proved that the shell of most species presents a granulated siu-face. I have therefore been obliged to alter its systematic position. The occurrence of two different kinds of mai'kings in the same genus is a remai'kable circumstance, but less enigmatical in this instance when we take into consideration that this genus represents the last type of the Trilobites, and therefore naturally would bring together characters which hitherto had been distributed over different contemporary genera. A similar combination takes place filso in Brontcus. The species may probably be grouped best in the following manner : I. Those in which the glabella has three lateral furrows, which obliquely extend towards the posterior part, and become gradually larger; the posterior and largest separates a lobe which is more strongly arched and more projecting ; and the elongated eyes corre- spond with the latter in position. The posterior angles of the cephalic shield are elongated in a granulated manner. — Phillipsia, Portlock. A. The glabella not broader towards the anterior part, but of the same breadth, and commencing from the eyes, afterwards parabolically rounded. The shell has a tuber- cular granulation, particularly at the axis. To this belong the species, Phill. Kcllii, Portl. {Rep. of Geol. etc., 307, Table II, Fig. 1) ; Pliill. oniata, Portl. (/. c. 307, Fig. 2) ; the figure in the same work marked Figs. 4. 10. 11. 12 ; the caudal shield in Brongniart's Crust, foss. Table IV, Fig. 12; Phill. gemmulifera, De Koninck, {Mem. de VAcad. Poy. de JBruxelles, torn, xiv. Fig. 3 ; Ej. Anim./oss. de la Belyiq. 603. 4, Table LlII, Fig. 3.) Perhaps we may also include among this group Amph. 102 SYSTEMATIC ARRANGEMENT duh'uix, Münster {Bei fr. 112, Table X, Figs. 1, 4, 5), togetlier with Cal. furcnfa (ibid. Fig. 9.) B. The glabella a little broader towards the anterior part, or at least broadly rounded, and more strongly arched at the extremity. The shell has a finer granulation, the eyes are very much elongated, and reach to the posterior margin of the cephalic shield. To this group belong, PhiUqma Jonesii, Portl. (30. 8, Table II, Figs. 3 and 5) ; Asaphus Balmanni, Emmr. {Dissert. 36. 21, Gold/, in Lconh. and Bronn. n. Jahrb. 1843, .561. 12) ; PJiiUipsia dnrlai/ensis, De Koninck {Anim. fossile, etc., 601. 2, Table III, Fig. 2) ; Cnlpnene ? cecjnalis, v. Meyer {Nova Acta Phijs. Med. Soc. Cues. Leop. Carol, n. cur. ,xv, 2. 100, Table LVI, Fig. 3). II. The glabella with only one lateral furrow, which separates one indistinct lobe before the margin of articulation. The eye shorter, but higher, more remote from the glabella, and not projecting so far towards the posterior part. — Griffithides, Portlock. a. The cephalic shield with horny, elongated angles, the surface of the shell at least partly granulated (e. g. on the cheeks). To this belongs Phillipsia (/lohieeps, De Koninck (599. 2, Table LIII, Fig. 1), and probably also Grißthides lonpsjnnm, Port). 312. Table XXIV, Fig. 12). b. The cephalic shield not elongated into processes, the surface of the shell without granulation, but with a lineated sculpture. To this belong two species: 1. A. ylobiceps, Mihi {Griff, glohiceps, Portl. 311. Plate II, Fig. 9 ; Asaph, r/lob. Phill. Geol. ofYorhh. 1, Table XXII, Figs. 16. 20 ; Emmr. Dissert, 35. 20). 2. A. daviceps, scuto capitis caudoeque subparabolico, angulis illius rotundatis ; axi caudae duodecies annulata, sulcis scuti lateralibus octo. Long. 1", Table V, Fig. 3. Archegonus ipqindis. Locality. — A grayish-brown grauwacke near Altwasser, in Silesia ; received (from the same locality) from M. Bocksch through M. de Charpentier ; in the Berlin Museum. The cephalic shield is somewhat broader than long, the glabella very convex, moderately thickened towards the anterior part, marked by deep, transversely corrugated lines, contracted in the region of the eyes, and there provided with a slight sulcation, which separates an indistinct lobe before the margin of articulation. The posterior extremity of the eye corresponds with this furrow. The margin of articulation projects somewhat at the posterior part ; the cephalic shield has, however, no reflexed, but only a slightly indicated marginal fold. The nine body rings are short, their lateral lobes rather broader than the axis, and very distinctly separated from it ; the oblique transverse furrow is very visible. The caudal shield is parabolic, rather convex, especially the axis, and obtusely rounded. We distinguish in it from ten to twelve rings, separated according to their size, and about eight more depressed lateral furrows, between which there may also be perceived the more shallow diagonal furrows. OF THE SPECIES. 103 SECTION II. TrUohites possessing the eapacifi/ of rollhif/ themselves up, the bochj axis not shortened posteriori!/, the shell finely lineated, the caudal shield not having radiated lateral farrows. — AsAPHin.E. I have already made some necessary remarks respecting the structure of the shells of this group ; an additional common characteristic, however, seems also to exist in the glabella, which is always simple and destitute of lobes, indistinct traces only of lateral lobes being occasionally recognized at its posteiior contracted part. The caudal axis likewise has frequently no joints, but generally has thera indistinctly marked, whilst the ribs on the sides of the shield are always entirely wanting, and are at the utmost only indicated by fine ridges or lines. With regard, however, to the width of the body rings I must remark that the central rings become rather broader than the anterior and posterior ones, and the axis has, therefore, only an equal width at the anterior and posterior part. A. Tlie body axis consisting of ten equal rings. Genus 17. — Ill^nus, (Ill^nus and Bumastes.) The cephalic shield may be best compared to the fourth part of a sphere, and is, therefore, bounded by curves on the posterior and anterior margins, and strongly arched between ; at the posterior margin we recognize the glabella as a slight convexity on the surface ; the anterior margin, on the other hand, is acutely angular, rather produced, and depressed. The facial suture projects obliquely over the flattened margin, rises with a gentle curvature upwards to the eye, forms the covering plate over the latter, and thence turns again with a gentle curvature towards the posterior margin, which it intersects not far from tlie axis. Both sutures are connected on the flattened anterior margin by a transverse suture. The eyes are semilunate, depressed, and smooth. The body consists of nine or ten short but broad rings, which are not furnished with an oblique transverse furrow on the lateral lobes. The large, almost semicircular, caudal shield is highly arched, and furnished with an indication of a short axis, as in Brontes. The surface of the shell has fine, concentric, irregular lines or ridges, between which, as also on the parts which are not striated, there are impressed punctures. Division A. — Axis of the body not broader than the lateral lobes, and distinctly sepa- rated from them. — Illj^inus, auctorum. The species occur in the lower strata of the grauwacke formation. 1. ///. crassicauda : Oculis margiui postico scuti ceplialici approximatis. Long. 1-3". Tab. V, Fig. 2. Entom. cr. Wahlenb. N. A. Ups. viii, 27. 2, Tab. II, Figs. 5, G. Dxhyi. Pal^ad. 51. 12, Tab. V. Fig. 2, «,/. Bronn, lefh. i, ll',, C. 3, Tab. IX. Fig. 9, a, b. Boeck, 104 SYSTEMATIC ARRANGEMENT Gaea Norw. i, 34. Emmr. Diss. 34. 17. Pander, Bcitr. 137, Tab. V. Figs. 9, 10. L. V. Buch, Beitr. 43. Triloh. Esmurkii, Schloth. Ms, 1826, 315, Tab. I, Fig. 8. Crjjpionymus Biidnljj]iü,^\cw.'W. Observ. etc. 50. ^ 56, Tab. II, Fig. 1, a, h. Cr. Mosenhergii, ibid. 48, Tab. Ill, Fig. 3, a, b. Or. Parkimonii, ibid. 51. ^ 57, Tab. IV, Fig. \,a,b. Cr. Wahlenhergii, ibid. 50, Fig. 3, a, b. Isotdes crassicauda, Milne Edw. Cr. iii, 300. 6. The following seem to be young individuals of the same species. Elanus perovali.'i, MuRCHis, Sil. Syst, iii, 661. PL XXIII, Fig. 7. Localiti/. — Occurs in the transition limestone of Sweden ; at Husbyfjol, in East Gothland ; at Osraundsberg, in Dalecarlia ; in Esthonia, at Revel, and at St. Petersburgh ; in England, in the Caradoc sandstones of Shropshire and Montgomeryshire. This common Trilobite is easily to be recognized by its peculiar habit, and is distin- guished from the following species by the eyes, which are situated far towards the posterior part, close to the borders of the head. 2. ///. giganteus : Oculis in medio latere scuti cephalici. Long. 3-6". Tab. Ill, Fig. 10. GUETTARD, Mem. do TAcad. Boy. etc. 1757, torn, xv. Tab. VII, Fig. 2 ; Tab. VIII, Fig. \; Tab. IX, Fig. 1. Occurs in the clayslate of Angers ; according to a specimen in the academical collection at Halle. This species seems rare, and not to have been found by any observer since Guettard's time ; it is, however, as distinct as any other species of Trilobite. The splendid specimen in the collection above named, of which I give an accurate figure, shows only the cast of the animal ; but exhibits all the characteristics of Ulanus, together witli the peculiarity which mai'ks it as a distinct species : this is seen in the position of tlie eyes, and is very manifest. The covering plate at each side of the cephalic shield is, however, only visible on the latter, the maxillary shield and the eye itself are wanting ; I have endeavoured to indicate its position by a dotted line. Division B. — The axis of the body comparatively broader, and only imperfectly sepa- rated from the lateral lobes by a slight longitudinal sulcation. — Bumastes, Murch. 3. IJl. (Bit.) burrieims ; Oculis margini postico scuti cephalici approximatis. Long. 2-3". MuRCH. Sil. System, ii, 656, PI. VII, Fig. 3, «, b, c, PI. XIV, Fig. 7. Jukes and Sowerby, Zoitd. May. of Mit. History, ii, 41. Silliman, ^'/ww. Journ. of Science, 1832, vol. xxiii, I. p. 203. Emmr. Dissert. 33. Milne Edw. Cr. iii, 295. Locality — The middle Silurian strata of England, at Barr, in Staffordshire, at Brandlodge, and Presteign. This Trilobite resembles so much the ///. crassicauda, with the exception of the body, the broad axis of which is not strictly separated from the lateral lobes, that I hesitated for some time before I could decide upon its being a different species. Isolated cephalic and caudal shields can scarcely be distinguished from the former. Remar/c. — Nilens glomerinus, Dalm. [Arsberatt, 1828, p. 136 ; Hising. Letli Sitec. 16), seems to be the same species. OF THE SPECIES. 105 B. The body axis cotmstinr/ of nine rings. Genus 18. — Dysplanus. Cephalic shield highly arched, large, semilunar, the posterior angles elongated into pointed processes, the glabella not more strongly arched, and no posterior j)roniinent margin of articulation. The facial suture describes in front a semicircle, bends towards the eyes, and extends with a gentle curve from the latter to the posterior margin ; between its extremity and the glabella there is at each side a furrow. Eyes small, slightly convex, scarcely rising above the level surface of the head, placed still further towards the exterior part than in Ulanns, lunate, transparently reticulated. Body axis rather convex, but the rings are short ; the lateral lobes rather broader than the axis, strongly bent downwards, without diagonal furrows. Caudal shield broad, semicircular, slightly arched, with a short, slightly indicated conical ixis, without rings or lateral furrows. The only known species is : D. centrofiis ; Asaph {Illesnus) centrot. Dalm. Pahead. 51. 11, Tab. V, Fig. 1, a. c. BoECK, Gaea Norm. I, No. 35. Emmr. Dissert. 34, 18. Isotcles centr. Milne Edw. Crust, 301. 7. LocaUti/. — The transition lime of Eastgothland, near Husbyfjöl, but of rare occurrence ; found also at Christiania. C. The axis of the body consisting of eight equal rings. Genus 19. — Asaphus, Brong. (Asaphus et Nileus, Dalm. ; Isoteles, Dekay ; Hejucrypturus, Green.) This genus embraces a widely extended group, if we define it according to the number of the rings of the body ; but in addition to these it only exhibits one other generic character, derived from the course of the entire facial suture, on the upper side of the cephalic shield. Intersecting the margin at the posterior part, in the centre of the lateral lobes, this suture turns with the usual S-shaped curve towards the eye, forms over it the covering plate, and thence extends, describing an arch to the centre of the anterior margin. The two angles pass into one another, describing a semicircle, if the anterior margin is obtuse, and they form an angle with one another if the latter is pointed. The eyes themselves are large, high, and exceedingly prominent, although not quite so elevated as in Thacops ; the thick horny membrane is smooth, but the lenses are not unfrequently seen through it. The axis of the body is of equal breadth, rather broader perhaps towards the centre, and usually distinctly separated from the lateral lobes ; the oblique transverse furrows are then visible likewise. The caudal shield resembles the cephalic, either wholly or very nearly in point of 14 106 SYSTEMATIC ARRAXGEMENT outline and shape, and has not always a projecting axis, but this axis, when visible, is usually articulated. Several subdivisions may be established in this large genus, and we may consider these as so many subgenera. Group A. The lateral lobes not separated by any furrow from the axis of the body and with no transverse furrows ; the trace of an axis wanting in the caudal shield, and the indication of the glabella in the cephalic shield. The facial suture describes a circle, the eyes are large, lunate, but not very prominent. — Nileus, Dalman. 1. AsapJms [Nileus) armadillo: Scuto capitis caudfeque convexo brevi dilatato ; angulis capitis -posticis obtusis: thoracis axi lobis lateralibus latiori. Loug. 1-2". Mef.—D^iM. Palcead. 49. 10, Table XIV, Fig. 3, a-e. Milne Edw. Crust, iii, 294. 1, PI. XXXIV, Figs. 1,2. P.\ND. Beitr. 132, Tab. V, Fig. 2. L. v. Buch, Beitr. 50. HisiNG. LetJi. Suae. 16, Tab. Ill, Fig. 3. Asaph, armed. Emmr. D'mcrf. 33, 15. Var. Minor : Nileus chiton. Pander, Beitr. 132, Tab. V, Fig. I. Milne Edw. Crust. iii, 295, 2. Locality.— '^\^& transition limestones of Eastgothland, Husbyfjöl, and Skarpasen ; in Dalecarlia, at Rathwick ; in Esthonia, at St. Petersburgh. Cephalic shield short, scarcely half as broad as long, uniformly convex, with rather acute margins ; the eyes separated far from one another, reaching almost to the anterior and posterior cephalic margins, but depressed, and with a large covering plate. The rings of the body short, without any division between axis and lateral lobes ; the former, however, is indicated, and is almost twice as broad as the latter, which has no trans- verse furrows. Caudal shield short, broad, curved at the basis, without a vestige of an axis. Remarks.^1. It is easily distinguished from Bumastes (like which, however, it has an axis not separated from the lateral lobes) by the number of body rings, and not less so by the position and size of the eyes, and the comparatively inferior size and less convex shape of the glabelhi. It stands, however, in the same relation to the following group as Bumastes does to Iltcenus, and, as in the latter case, there are analogous forms. 2. Nil. gJomerinus, Dalm. (Arsberatt 1828. 136; Risinger, Let h. Siiec. 16). Nil. glaberrimus (Milne Edw. Cr. iii, 295), with small eyes and ten body rings, may probably be identical with Bumastes barriensis. Dalman's specimens were found at Husbyfjöl. Group B. The lateral lobes of the rings of the body separated from the axis by a depressed longitudinal furrow. The diagonal furrows of these lobes seem to be always present.* Subdivision A. — The facial suture describes an arch anteriorly, but is not angular. a a. The glabella and caudal axis distinctly indicated, the latter not articulated and very short (?). The eyes are also flatter and depressed, lunate, and supported at the lower part by a portion of the cheek-shield, upon which they are borne ; the diagonal furrows of the lateral lobes appear to be slight. — Symphysurds, Goldfuss. * They have not been indicated in Dalman's figure in Asaph, palpebrosus and A. Imviccps, but are mentioned in the description as being slight. OF THE SPECIES. 107 2. As. palpebrosiis : \'crticc tumido, uiargiuem crassum scuti ccphalici superantc ; oculis longis- simis. Long. IK-li'i ". Dalm. Falaad. 48. 9, Tab. IV, Fig. 1, a-c. Emmr. Dimcrt. 32. 14. Milne Edw. Crust, iii, 299. 4. Hising. Ldh. Sure. 1.5, Tab. Ill, Fig. l.ajj. Localily. — The transition limestone of Eastgothland, at Husbyfjül. Having had no oppor- tunity of examining a specimen of this or the following species, I must refer the reader to Dalman's detailed description. 3. As. l5. signatus, Ph. See Appendix, p. 119. Bu.MA.STES, Murch. ■ Barriensis, Murch. Iltenus barriensis, p. 104. C.ALYMEXE, Brong. Blumenbachii, Brong. Ibid. p. 81. brevicapitatus, Portl. Downingife, Murch. Phacops macrophthalmus, p. 92. granulata, Munst. Phacops latifrons, p. 87. laevis, Munst. Phacops Itevis, p. 89. Latreillii, Stein, multisegmentatus, Portl. pulchella, Dalm. Calymene Blumenbachii, var. p. 82. Sternbergii, Munst. Cheirurus sp. p. 71, note, tuberculata, Murch. Phacops latifrons, p. 89. variolaris, Brong. See p. 83, note, and p. 114. Ceraurus, Green globiceps, Portl. EuRYPTERUS, Harlan. Scouleri, Hibbert. Se Griffithides, Portl. globiceps, Portl. longiceps, Portl longispinus, Portl. platyceps, Portl. 54. See Archegonus, p. 101 and Appendix, p. 1 12. Harpes, Goldf. Doranni, Portl. See p. 75, note. Flanaganni, Portl. See p. 75, note, macrocephalus, Goldf. See p. 75. HOMALONOTUS. Kouig. delphinocephalus, Murch. Ibid. p. 56. Ilerschelii, Murch. Ibid. p. 87. Knightii, König. Ibid. p. 86. Ludensis, Murch. Under II. Knightii, p. 56. Ill^f,nu.s, Dalm. centrotus, Dalm. Dj-splanus centrotus, p. 105. crassicauda, Dalm. Ibid. p. 103. ? perovalis, Murch. I. crassicauda junr. ? p. 104. quadrato-caudatus, Portl. IsoTELEs, Dekay. arcuatus, Portl gigas, Dekay. Asaphus platycephalus, p. 110. intermedius, Portl. lasviceps, Portl. ovatus, Portl. palpebrosus, Dalm. p. 107. planus, Dekay. Powisii, Portl. See note p. 96 (includes Pha- cops felinus, Salter), rectifrons, Portl. sclerops. Green. NuTTAiNiA, Eaton. Hibernica, Portl. Lichas sp. p. 66, note. ? obscura, Portl. Ogygia, Brong. Murchisoniae, Murch. Ogygia Guettardi, p. 60. rugosa, Portl. Paradoxides, Brong. ? Bucephali, Portl. bimucronatus, Murch. Chirurus sp. p. 71, note, quadrimucronatus, Murch. Odontopleura ellip- tica, p. 63. Olenus, Dalm. punctatus. Stein. Phacops, Emmerich. Brongniartii, Portl. Phacops latifrons, p. 88. Dalmanni, Portl. Jamesii, Portl. Murchisonii, Portl. truncato-caudatus, Portl. Phillipsia, Portl. Jonesii, Portl. Kellii, Portl. Maccoyii, Portl. obsoleta, Phil, ornata, Portl. raniceps, Phil, seminifera, Phil. See Archegonus, p. 101, and Appendix, p. 112. SUPPLEMENTARY APPENDIX. 123 REMOPLEuiiinr;s, Portl. p. llö. Colbii, Portl. dorso-spinifcr, Portl. lateri-spinifcr, Portl. longi-capitatus, Portl. longi-costatus, Portl. Trinucleu.s, Lhwyd. ? Asaphoides, Murch. Sec remarks, p. 58. Caractaci, Murch. Ibid. p. öö TuiXUCLEUS elongatus, Portl. fimbriatus, Murch. Ibid. ]). .5". latus Portl. Lloydii, Murcli. T. granuiatus, p. .57. nudus, Murcli. an Am/ii/i-. (uote, p. 57). '! punctatus, Murch. radiatus, Murch. Trinuclcus ornatus, p. seticoriiis, Portl. p. 58. 58. II. To the above List of British Trilobites must be added tliosc species described since the publication of Mr. Morris's Catalogue, and wliicii have not come under the inspection of Professor Burmeister. In Mr. M'Coy's ' Synopsis of tlic Carboniferous Fossils of Ireland,' the following new species are described and figured : ■" Griffithldes calcaratus. Phillipsia coelata. Phillipsia Colei. Phillipsia (?) discors. Phillipsia mucronata. Phillipsia quadriserialis In Mr. M'Coy's ' Synopsis of the Silurian Fossils of Ireland,' collected by Mr. Griffith (Dublin, 1846), the following new genera and species are described and figured : TiRESiAS. New genus. " Cephalo-thorax semioval, longitudinal ; glabella very gibbous, pyriform, rounded in front, contracted into a narrow neck posteriorly (obscure traces of two small cephalo-thoracic furrows on each side) ; neck furrow very strong; cheeks triangular, gibbous, prolonged backwards into long flattened spines; eyes none?" " This remarkable Trilobite agrees nearly in form with the carboniferous genus Griffithides, Portl., except in being apparently Wind." (Loc. cit. p. 43.) One species, T. imculptus, in the limestone of the Chair of Kildare. FoRBESiA. New genus. [From the description and figures this genus would appear to be synonymous with Proetus.] F. latifrom. PoRTLOCKiA. New gcnus. Cephalo-thorax truncato-orbicular, lateral angles not produced into spines ; glabella large, clavate, widest in front, reaching to the margin, contracting to a narrow neck behind ; neck fuiTow strong ; cheeks rather small, triangular, convex ; eyes large, reniform ; abdomen of thirteen segments, rounded at their extremities, anterior margin sharpened for contraction ; pygidium semi-elliptical, of seven simple segments ; margin entire, smooth. The genus includes CuJymene fubercuhtla and C. marroj)IifIiahiia of the Silurian S3'stem ; Fhacops tuhercuJaia of Captain Portlock's report ; Calymene nvpera, Hall ; Calymene hufo. Green, &c. * In the same work are described and figured the following allied Crustacea from the cai'bouifcrous limestone of Ireland : Dithyrocaris (Scoular) Scouleri ; Entomoconchus (new genus, M'Coy) Scouleri ; Cytherina Phillipsiana of De Koninck; Daphnia primjEva; Bairdia (new genus, M'Coy) curtus. B. gracilis ; Cythere amygdalina, C. arcuata, C. bituberculata, 0. costata, C. cornuta, C. elongata, C. excavata, C. gibberula, C. Hibbertii, C. impressa, C. inflata, C. inornata, C. oblonga, C. orbicularis, C. pusilla, C. scutulum, C. spinigera, C. trituberculata. 124 SUPPLEMENTARY APPENDIX. Trinodus. New genus. Cephalic shield truncato-elliptical ; glabella convex, nearly cylindrical, sharply defined ; cephalo-thoracic furrows, one on each side confluent with the next furrow, and with that defining the glabella, rctroflexed to fonn a small flattened tubercle on each side of the base of the glabella ; neck segment small, narrow, convex, surrounding the glabella in front, the portion in front of the glabella as wide as that at the sides ; cheeks surrounded by a thick, flattened, entire margin, of equal width all round ; eyes none, facial suture (? none) ; caudal shield equal, and similar in form to that of the head ; axal lobe semicylindrical, very convex, divided by three segmental furrows, and having usually a prominent, lengthened tubercle extending down the middle, and which is not cut by the segmental furrows ; lateral lobes almost equal to the axal, very convex, not marked by the segmental furrows ; portion encircling the obtuse apex of the axal lobe about equal to that of the sides, surrounded by a flattened margin, less than the side lobes in width." T. agnosiifonnis. Remopleurides laticeps. Acidaspis bispinbsus. Sphffirexochus calvus. [Calymene clavifrons of Dalman.] Encrinurus Stokesii. [Calymene variolaris of authors.] Calymene arenosa. Calymene ? forcipata (a Lichas?). Portlockia sublaevis. Lichas laxata. Lichas pumila Ilomalonotus ophiocephalus. Otarion obtusum. Harpes ? megalops. Mr. M'Coy, in the same work, has placed the Balfiis tubercidafus of Kloden among the Entomostraca, in a genus which he names Beyrichia, and defines as follows : " Gen. Char. Shell bivalve, rotundato-quadrate, ventral margin slightly concave, ends very nearly equal, obtusely rounded ; sides equal, very gibbous, deeply impressed by a strong and wide sulcus, which extends fi'om the ventral margin nearly to the dorsal, giving a bilobed or reniform appearance to each valve ; sulcus slightly nearer to the anterior end ; within this sulcus on each valve, and close to the anterior (or smaller) side, is a lengthened oval tubercle, nearly at right angles with the ventral margin, and reaching about two thirds of the distance from thence to the dorsal margin ; surface smooth. " On first examining some specimens from the Irish Silurian sandstones, of what I considered to be the Aynostus {Batfus) tuheradotiis, Klod., of the Silurian System, I perceived that the vertical sulcus was very slightly nearer to one end than to the other, and that the lengthened tubercle forming the so-called mesial lobe was not precisely in the middle, as figured and described by authors ; this deviation, though very slight, was important, as showing that we could not be really looking at the back of a symmetrical animal, as was previously supposed, and that the creature could not be an Agnosim. I also perceived that some of the specimens had the tubercle nearest the right, and others nearest the left end, and that consequently I had got the two valves of an entomostracous shell. I therefore doubted the correctness of the reference to the English species until, on examining the original specimens in London, I found that they too were unsymmetrical ; I am now therefore certain that my observations apply equally to the Irish fossil and the Agnosius tuherculafus of Wales, but should still have doubted the reference to Kloden's Brandenburg species, had not an author well acquainted with the continental fossil published, a few months ago, a Memoir, in which he incidentally alludes to this subject, and expresses an opinion of Kloden's SUPPLEMENTARY APPENDIX. 125 continental fossil, similar to that I had already formed of the English and Irish specimens, and which though I cannot advance as a discovery, I can yet confirm so far. To o-ive Herr Beyrich full credit for his penetration, I subjoin his remarks (loc. cit. p. 47), and have great pleasure in naming the genus after him. ' Baftus tubcradalus, Klöden, welchen Burmeister als synonym zu Odontoplciira omtu citirt, ist weder ein Battus nocht überhaupt ein Trilobit. Er hat ein zweiklajjpige Schale, deren Oberfläche mit ganz unsymmetrisch geordneten Lappen und Tuberkeln bedeckt ist, und muss eine besondere Gattung neben Cytherma bilden.' " The Af/nostus Mus of the American geologists from their ' Clinton group,' also belono-s to this genus. The species I propose naming after its original discoverer, Bcijrichia Klodeniy (Loc. cit. p. 58.) The Cythere jjliaseolus of Hisinger is enumerated among Irish Silurian fossils in the same work. IV. The following new Trilobites and Entomostraca are described and figured by Mr. Salter in the work of Professor Sedgwick, already mentioned.* Cheirurus juvenis. Cybele sexcostata. Calymene tuberculosa. llhenus Davisii. Bowmanni. Asaphus elevatus. Homalonotus bisulcatus. parvifrons. rudis. Lichas (nodulosus) ? Cephalaspis. Ogygia radiata. Dahuannia aifinis. Agnostus trinodus. obtusicaudata Beyrichia complicata. Phacops apiculatus Beyrichia plicata, felinus. Cythere umbonata. alifrons. Cypridina strangulata V. From the treatise ' Ueber einige böhmische Trilobiten,' by Dr. Ernst Beyrich (1845), referred to by Professor Burmeister more than once, we have extracted the following generic characters of Cheirurus, Sph.erexochus, Lichas, and Trochurus. Cheirurus. Caput ambitu semi-orbiculari, limbo prsecinctum, testa tectum granulosa in glabella, scrobiculosa in genis. Suturse faciales ab oculis postice ad marginem exteriorem, antice sejunctse ad marginem ductae. Oculi parvi. Sulcus occipitalis profundus, prope angulos cum sulco marginali confluens. Glabella magna, lata, usque ad limbum marginalem porrecta, frontem versus dUatata. Sulci laterales glabella; tres distincti ; posteriores versus ad sulcum vertiealem retrorsi ; medii et anteriores ssepius conjuncti, recti vel parum retroversi. Alse occipitales scuti centralis latae ; scuta marginalia parva. Thorax ex articulis, undecim. Rhachis arcuata, versus pygidium coarctata, trans- versim annulata. Pleurse sulco transversal! in partem interiorem minorem et exteriorem * In the forthcoming (the second) volume of the Memoirs of the Geological Survey of England and Wales, now in the press, a new species of Olcints is described by Professor Phillips, under the name of O. Iiumi/is, and a new A»ipi/x, named by Professor E. Forbes, A. purvuhm. 126 SUPPLEMENTAEY APPENDIX. majorem dmsse ; pars interior sulco longitudinali oljliquo cxarata, pars exterior Integra recurva. Pygidium breve, latum^ digitato-fissum, compositum ex articulis tribus completis et articulo quarto tcrminali pleuris carente. Pleurae majore ex parte liberse ; anteriores sulco brevi longitudinali exaratte seque ut tlioracis pleuras. (Three new species, C. insiffnis, C. damyer, and C. r/ibhus.) Sph^rexochus. Caput ambitu semi-orbiculari (limbo praecinctum?) testa tectum undique granulosa. Suturae faciales ab oculis postice ad mai-ginem exteriorem prope angulis, antice sejunctse ad marginem ductse. Oculi cornea rotundata distinctae granulosa (Loven.) Sulcus occipitalis latus profundus. Glabella magna, antice usque ad marginem producta, inde a sulco verticali turgida, suliliemispliasrica. Sulci laterales onmes sejuncti, posteriores reversi, saepius cum sulco verticali confluentes ; anteriores et medii recti, sejuncti, saepius obscuri. Thorax ex articulis undecim. Pygidium breve, latum, digitato-fissum, compositum ex articidis tribus completis, quonmi postremus in rhachi penitus implicatus est cum articulo terminali. Pleurae elevatse; sulcis profundis sejunctse, apicibus liberis. {Sphmrexochus mirns. ) LiCHAS. Caput testa tectum undique dense granulosa. Suturae faciales ab oculis antice sejunctae ad marginem ductae ; postice (?) Glabella lata usque ad marginem porrecta, fronte plerumque tumida margini imminente. Sulci laterales anteriores retroversi, longissimi, sejuncti proximo ad sulcum verticalem retroducti ; medii saepius obsoleti, posteriores breves, retroversi, cum sulco verticali confluentes. Thorax ex articulis undecim, pleuris planis, falcatis, sulco longitudinali usque ad apicem acutum exaratis. Pygidiiun ambitu laciniato, compositum ex articulis tribus completis, quorum postremus in rhachi obscure distinctus est a medio et penitus implicatus cum articuli terminali. Pleurae sulcis sejunctae et sulcis longitudinalibus exaratae, apicibus anteriorum et mediarum (in quibusdam speciebus posteriorum quoque ?) liberis. (Two new species, LwJias scahra and L. dissidens.) Trochurus. Caput ambitu semi-orbiculari, testa tectum undique granulosa. Suturae faciales ab oculis postice ad marginem exteriorem prope angulos ductae ; antice ? Oculi ? Glabellae pars anterior (frons) valde dilatata, turgida, subhemisphaerica, usque ad marginem porrecta ; pars posterior angusta, semicylindracea, sulcis dorsalibus parallelis definita, stipitem quasi frontis exhibens. Sulci laterales posteriores et medii obsoleti, anteriores conjuncti ; sulcus occipitalis profundus. Thorax ex articulis undecim f Pygidium ambitu semi-orbiculari ; lateribus planis ; rachi convexa, versus marginem angustata et attenuata ; margine spinis sex tenuibus pendulis aucto. Rhachis antice annulos articulorum duos praebet, sulcis profundis sejunctos. Pleurae utrinque tres distinguendas ; anteriores et mediiE costis definitas, rectis, radiantibus, ad spinas marginis ductis ; posteriores costis carentcs, cum rhachi coalitae, prope rhachim spiniferae. Testa granulis inaequalibus scabra. (One species Trochurus sjjeciosus.) VI. M. Joachim Barrande has very recently (1S46) published a memoir, entitled SUPPLEMENTARY APPENDIX. 127 ' Notice Preliniinaire sur le Systeme Siluricn ct les Trilobites dc Boheme.' In this paper a very great number of new species of Trilobites are briefly described, but not figured, and several new genera noticed. With a view to prevent over-multiplication of synonyms, and to render this enumeration as complete as possible, we .extract the new names given in M. Barrande's treatise, and refer the reader to the work itself for the descriptions. In the following- list the names of the new genera are printed in small capitals. Aretiiu.sa Koninckii Abiox ceticephalus Asaphus ingcns nobilis (Nileus) Bouchardi Battus bibullatus granulatus Orion af&nis rex cuneifer tardus Bronteus Brongniarti porosus pustulatus formosus angusticeps Zippei Partschii Haidingeri ambiguus Caphyra radians Calymene pulclira parvula incerta diademata Bayleii Beaumonti Cheirurus Beyrichii Quenstedti corda Conocephalus Emmerichii coronatus Cyphaspis Burmeisteri depressa Cerberus DioxE Formosa Egle rediviva Ellipsoccphalus nanus tumidus Harpes tenuipunctatus Hydrocephalus Saturnoides carens Lichas propinqua pahuata simjjlex Haueri parvus MoNADlNA distincta micron Odontopleura Prevosti Dufrenoyi mira Verneuili Leonhardi minuta tricornis direlicta Hornesii lacerata Buchii primordialis Proetus Ryckholtii intermedius decorus venustus lepidus luberculatus Myops inasquicostatus sculptus gracilis Lovenii Phaeton membranaceus striatus Archiaci Paradoxides Linnei rotundalus pusillus Phacops fecundus bulliceps trapeziceps 128 SUPPLEMENTARY APPENDIX. Phacops Glockeri intercostatus spinifer Reussii Bi'onnii socialis Hawlei elongatus 'dubius Philiipsii intermedius breviceps Phacops laivigatus Sao hirsuta Staürocephalus Murchisoni Trinucleus Goldfussii Bucklandii Trilobites heteroclytus orbitatiis desideratus decipiens Lindaueri. DESCRIPTION OF THE PLATES. TABLE I. Fig. 1. Triimdcus Caractaci. 2. 0()i/(jia Biichii. 3. Guettardi. 4. Oclontopk'ura elUptica. 5. Paradoxides hohtnücm, old specimen. 6. Bo. do. young. 7. Bo. do. under part of cephalic shield (irtc/^a/as). 8. EUijJsocephalm Hoßi. 9. CoHOcephahis driatas. 10. Sulzeri. 11. Harpcs ungula. 11«. A portion of the sculptiu'c of the margin magnified. TABLE IL Fig. 1. CulymeHc Bhtmenbachii, rolled up, vie\Aed from the side, drawn from a perfectly-preserved specimen in M. E. Anton's collection. 2. The same, extended, seen from above. 3. The same, a front view. 4. Phacojjs lafifrons, rolled up, side view. 5. The same, extended, from above. 6. The same, front view. 7. Cephalic shield of Calymene Tristani, from above. 8. The same, from the side. 9. Cephalic shield of Calymene calliccpliala, from above. 10. The same, from the side. 11. Odoniopleura ovata. 12. Asapkm p)latycephalus. 17 130 DESCRIPTION OF THE PLATES. TABLE III. Fig. 1. Proetus Cuvieri, Gerastos lavigatus, Gold!"., rolled up, side view. 2. The same, extended, from above. 3. Ci/phmpis ceratopldhalma, rolled up, side view. 4. The same, extended from above. 5. Aeonia diops {Calj/mene diops. Green). 6. Phacops protuberans. 7. Tril. Sternhergii, cephalic shield from the side. 8. The same, from above. 9. Olctms (jihhosus. 10. lUanus ijigantem. TABLE IV. Fig. 1 . Homalonofiis armatus. 2. Phacops rotundifrons. 3. Phacops proavus, cephalic and caudal shield. 4. odonfocephaliis, head. 5. conophihalmus. 6. The same, rolled up. 7. Phacojjs arachnoides. 8. stell if er. 9. caudal us. 10. Four body rings of Homalonotus as seen in a transverse section. 11. Four body rings of Calymene as seen in a transverse section. Remark. — The anterior smaller segment in these two transverse sections, represents the articular fold; the posterior larger segment indicates the true ring, beneath which the articular fold is hidden when the body is ex- tended. In Catymene we merely perceive an acute angle at the place where the two segments meet ; in Homalonotus, on the other hand, a thick, perpendicularly-descending ridge. 12. The eye of Phacops latifrons, without a horny membrane, enlarged to twice its natural size. TABLE V. Fig. 1. Asaphns cxpansus. a. Extended. b. Rolled up, and seen in front. c. Do. lateral view. 2. nianus crassicauda. a. Extended. Ij. Rolled up, front view. DESCRIPTION OF THE PLATES. 131 Fig. 2. c. Rolled up, side view. Eemark. — Particular attention has been paid to the sculpture in both figures, and the body has therefore been represented only in outhne. 3. Arcliegonus claviceps. 4. Caudal shield of Asaphws Tijrannus. 5. Aeonia Slokesii, cephalic shield. 6. ^/^»o.y/«« jöM{/bn«/s, cephahc shield. 7. The same, caudal shield. 8. Aeonia concinna. 9. Aeonia verticalis, Gerastos cornutus, Goldf. 10. Pkacojjs Ilaiismanni. Remark. — Two forms of the caudal shield of this species occur in the grau- wacke hmestone of Bohemia, of which the one, which is the rarer species, is more elongated, and has 21 joints of the axis, upon which two larger tubercles are placed near the centre. The lateral lobes, 1 5 in number, are broader, more depressed at the upper part, less distinctly impressed longi- tudinally, and the granulation of the siu-face is more scattered. The other form (represented here) is shorter, broader, and more obtuse; has only from IS to 19 rings in the axis, and 13 more convex and narrower lateral ribs, which are distinctly furrowed at the angle, and very finely, and, on the axis, uniformly granulated. I suspect that the former form may have been the male, the latter the female individual. TABLE VI. Fig. 1. AjMS cancriformis, viewed from below, natural size, very old. 2. Serolis paradoxa, from above, fuU grown. 3. Brancldpus stagnalis, from below, enlarged to six times its diameter. 4. Structure of the eyes oi BrancMjMs. a. Cornea extern, laivis. b. Cornea ai-eolata. c. Lens. d. Corpus vitreum. e. Commencement of the black pigment. /. Nervus opticus. 5. Parts of the mouth of Avus. A. The jaw. B. 1 P. The accessory parts of the mouth. C. 2 P. Do. do. D. Rudiment of the first foot. 6. Parts of the mouth of Brancldpus. A. The jaw. D. Rudiment of the fijrst foot. 132 DESCRIPTION OF THE PLATES. Fig. 7. Imaginary transverse section of an Amphus. a. Lateral lobes of the shell. h. The gül. c. The most external fin lobe. d. Interior do. 8. View of an Amphm cornigcrm, from below. a. Clj'peus. hh. Lobi antennigeri. cc. Lobi laterales. d. Labrum. pp. Mandibular. ff. The indentations into which the lower ends of the lateral lobes are placed when the animal rolls itself up. h. Rectum. 9. Foot of an Apus cmicriformis, from the body region, \ery nuicli enlarged. 10. Foot of the same species, from the central region of the tail, very much enlarged. 11. The last foot of Apiis cancrifonnis, very much enlarged. 12. Foot oi BranchijJiis stcif/naUs, very much enlarged. The designation of each of the feet is as follows : A. Basis, where it is aifixed to the body. B. Basis interna libera. 1 — 5 Fin lobes. K. Gill. L. Lobe protecting the gill. /. Second protecting lobe. . 13. A young Apus. a. Small feelers. b. Large feelers. c. Jaw. d. Rudiments of the feet. 14. Young Branchipus : parts as in the last. 15. Linniadia mauritiana, enlarged. B. Foot of Limnadia, parts as above. 16. Branchipus, with a Trilobite shell, viewed from above. INDEX OF GENERA AND SPECIES ENUMERATED BY THE AUTHOR. AcASTE, Goldfus«, 88. AciDASPis, Murcli. 61. Brightii, 63. AcTINURUS, 66 Aeonia, Biimi. 99, 100. coneinna, 100. Stokcsii, 100. verticalis, 100. diops, 100. Agnostus, 116. pisiformis, 117. laevigatus, 117. integer, 117. nudiis, 117. Amphion, Pand. 79. froutilobus, SI. gelasinosiis, 71. Ampyx, Dalm., 110. incertus, 112. mammillatus. 111. nasutus, 110. ? pachyrhyuchus, 66. rostratus. 111. Anthes, 72. Apcs, 41. Archegonüs, 101. centrotus, I0.>. seqvialis, 102. globiceps, 102. Arges, Goldf. 6.3. armatus, 63, 64. radiatus, 63. planospinosus, 7 1 . .\btemia, 41. AsAPHüs, Brong. 10.). angustifrons, 110. ai-achnoides, 96. ASAPIIIS, armadillo, lOti. astragolites, 96. aiiriculatus, 94. breyis, US. Brongniartii, 112. Buchii, 59. caudatus, 94. Cawdori, 117. centrotus, 105. claviceps, 102. corndeusis, 61, 113. cornigeriis, 107. crypturus, 95. Cyllarus, 58. Dalmanni, 102. dilatatus, 59. diurus, 118. dubius, 99, 102. duplicatus, 61. expansus, 107. exteniiatus, 109. Fisclieri, 81. frontalis, 113. gemmuliferus, 1 12. gigas, 110. globiceps, 102, 112. grandis, Sars, 107, 118. Munster, 111. granulatus, 57. granulifems, 1 1 2. Hausmanni, 93. heros, 112. laciuiatus, 66. Ifpviccps, 107. laticauda, 65. laticostatus, 95. ASAPHUS, limulurua, 95. longicaudatus, Oö. megalophthalmus, 1 1 2. micrui-us, 95. mucronatus, 94. myimecoides, 96. obsoletus, 112. palpebrosus, 107. platycephalus, 110. platynotus, 112. pleuroptyx, 95. Powisii, 96. pusUlus, 118. quadrilimbatus, 112. raniceps, 109. selenurus, 95. seminiferus, 1 12. seticornis, 58. Stokesii, 100. subcaudatus, 1 18. tetragonoeephalus, 70. Trimbii, 113. truncatulus, 112. tuberculato-caudatus, 94. Tyrannus, 108, 113. Vulcani, 113. Wetherillii, 90. Zinckenii, 120. Battus, 117. pisiformis, 117. integer, 117. nudus, 117. tuberculatus, 62. Beanchipus, 41. Brongniartia, 110. carcinoidea, 1 lU, 116. i;34 INDEX OF GENERA AND SPECIES. Bromtes, Goldfuss, 64. costatus, 65. flabeUifer, 65, 119. fiireata, 118. glabratus, 119. laticauda, 65. Neptuni, 65. radiatus, 65. signatus, 119. subradiatus, 65. Bum ASTES, Murcb. 104. bamensis, 104. franconicus, 118. planus, 118. Calymene, 79. sequalis, 102. actinura, 68, 83. anchiops, 83, 90. articulata, 71, 116. aracbnoides, 96. bellatiüa, 83, 99. Blumenbachii, 81. bufo, 83, 88. caUicephala, 83. clavifrons, 99. concinna, 83, 100. > decipiens, 74. diops, 83, 100. Downingise, 83, 92. frontiloba, 81. furcata, 118. granulata, 89. hydrocephala, 98, 120. intermedia, 112. Jordani, 89, 119. lievis, 89. latifi'ons, 88. macrophthalma, 83, 88, 92. microps, 83, 91. odontocephala, 83, 92. ornata, 112. phlyctsenoides, 112. platys, 82. polytoraa, 81. propinqua, 71, 116. protuberans, 89. punctata, 83, 114. Scblotheimii, 88. Schuster!, 120. sclerops, 83, 91. Calymene, selenecepbala, 83. speciosa, 71. Sternbergii, 71, 116. Stokesii, 83, 89. subornata, 120. Tristan!, 80. tuberculata, 83, 89. variolaris, 79, 83, 114. verrucosa, 99, 112. Ceraukus, Green, 61. crenatus, 63. Crosotus, 63. globiceps, 63, 71. pleurexanthemus, 63. Cheirurus, 71. Conocephalus, Zenk. 72. costatus, 73. striatus, 73. Sulzeri, 73. Cryph.eus, Green, 113. callitelus, 113. Boothii, 113. Cryptolithus, Green, 56. Bigsbü, 58. tesselatus, 58. Cryptonymus, Eich. Lichtensteinii, 107. Panderi, 107. Parkinsonii, 104. Eosenbergii, 104. Eudolphii, 104. Scblotheimii, 107. Wahlenbergii, 104. Weissii, 109. Cypuaspis, 98. clavifrons, 99. ceratoplithalma, 98. Cyprts faba, 50. Cybele, Löev. 99. beUatula, 99. verrucosa, 99. Cytherina, 55. . baltica, 55. phaseolus, 55. DiPLEURA, Green, 85. Dekayi, 85. Dysplanus, 105. centrotus, 105. EiDOTEA, Scouler, 54. Ellipsocephalus, Zenk. 74. ambiguus, 74. Hoffii, 74. Entomolitiu's, Linn. Derbiensis, 112. expansus, 107. paradoxissimus, 68. paradoxus, 82,107. pisiformis, 117. tuberculatus, 82. En'tomostracites, Wahl. actinurus, 69. bucephalus, 68. caudatus, 94. crassicauda, 103. expansus, 107. exteuuatus, 109. gibbosQS, 70. granidatus, 57. laciniatus. 66. laticauda, 65. paradoxissimus, 68. pisiformis, 117. punctatus, 114. Estheria, Strauss, 41. EuRYPTERUs, Dekay, 54. lacustris, 54. remipes, 54. tetragonophthalraus, 54. Scouleri (Eidotea), 54. Gerastos, Goldf. 99. cornutus, 100. globiceps, 102. granulosus, 100. Isevigatus, 100. sphisericus, 100. GoLDius, 65, 120. flabeUifer, 63. Griffitiiides, 102. globiceps, 102. longispinus, 102. claviceps, 102. Harpes, Goldf. 74. macrocephalus, 75. speciosus, 75. ungula, 75. Flanaganni, 75. Doranni, 75. Hemicrypturus, Green, 105. Rasoumowskii, 107. INDEX OF GENERA AND SPECIES. 135 HoMALüNOTVS, König. 84. Alirendü, 86, 120. armatus, 8". Dckayi, 88. delpbinoccplialus, 86. gigas, 120. Greenü, 87. Herschelii, 87. Knightii, 86. ludensis, 86. punctatus, 120. Ill.knus, 103. barriensis, 104. centrotus, 106. crassicauda, 103. giganteus, 104. perovalis, 104. IsoTELEs, Dekay, lOä. angustifrons, 1 10. centrotus, 105. crassicauda, 104. Cyclops, 1 10. dilatatus, 59. expansus, 107. extenuatus, 109. gigas, 110. Iseviceps, 107. Liclitensteinii, 107. megalops, 1 1 0. megistos, 120. palpebro.sus, 107. planus, HO. Powisii, 108. stegops, 1 10. Lepidurus, 41. LiCHAS, Dalm. 66. laciniatus, 66. LiMNADIA, 41. LiMULUS, 35. Metopias, 66. Nileos, Dalm. 11)6. armadillo, 106. chiton, 106 glaberrimus, 106. glomerinus, 104, 106. NuTTAiNiA, Eatou, 58. concentrica, 58. Hibernica, 66. Odontopleur.v, Em. 61. elliptica, 63. ovata, 62. Ogygia, Brongn. 59. Bucbii, 59. Desmarcsti, 60. Gucttardi, 60. Murchisonii, CO. Olenus, Dalm. 69. alatus, 70. Bohemicus, 69. bucephalus, 68. forficula, 70, 72. gibbosus, 70. gracilis, 67. latus, 67, 70. pyramidalis, 67. punctatus, 96. scarabseoides, 72. spinulosus, 68. Tessini, 67, 68. Otarion, Zenk. 58. diffractum, 58. elegans, 75. pygmaeum, 75. Pauadoxides, 66. acuminatus, 70. alatus, 70. arcuatus, 72. armatus, 116. bimucronatus, 71. Boltoni, 66, 68. bobemicus, 67. brevimucronatus, 1 18. bucephalus, 68. forficula, 70, 72. gibbosus, 70. gracilis, 67. Grotei, 96, 120. Harlani, 68. latus, 67, 70. longicaudatus, 67. pyramidalis, 67. quadrimucrouatus, 63. scarabseoides, 72. spinulosus, 68, 72. Tessini, 67, 68. triarthrus, 72, 116. Peltura, M. Ed. 88. Bucklandi, 97. scarabseoides, 71. Phacops, Emm. 88. anchiops, 90. arachnoides, 96. PlIACOPS, caudatus, 94. ceratoplithalmus, 98. clavifrons, 71. conophthalraus, 91. Hausmanni, 93. latifrons, 88. macrophthalmus, 92. miicrouatus, 94. odontocephalus, 92. proasvua, 93. protuberans, 89. rotundifrons, 92. selerops, 91. sphairicus, 99. stcllifer, 97. Tariolaris, 114. Phillipsia, Porti, derlayensis, 102. gemmulifera, 101. globiceps, 102. Jonesü, 102. Kellii, 101. oruata, 101. Platinotus, 66. Pleuracanthus, M. Ed. 88. arachnoides, 96. laciniatus, 92. punctatus, 96. Proetus, Stein. elegantulus, 98. Cuvieri, 99. concinuus, 100. granulosus, 100. Remopleurides, Porti. 116. Serolis, Leacb, 35. Sph.erexochus, 99. Symphysürus, 106. Triarthrus, Green, 116. Beckii, 72, 116. Trilobites. Aaellus, 119. Blumenbachii, 81. bobemicus, 67. Buchii, 59. bucephalus, 68. caudatus, 94. cnrnigcrus, 107. crassicauda, 103. dentatus, 119. 136 INDEX OF GENERA AND SPECIES. Trilobites, Desmaresti, 60. dilatatus, 59. elliptifroDs, 119. elegans, 119. Esmarkii, 104. gibbosus, "0. gracilis, 67. Guettardi, 60. Hausmanni, 93. Hoffii, 74. laciniatus, 66. latieauda, 6.T. latifrons, 88. longicaudatus, 67. macrophthalmus, 83. minor, 67. mucronatus, 94. omatus, 58. parado.xus, 82. pisiformis, 117. punctatus, 114. TaiLOBITES, scarabseoides, 72. Schroten, 108. semilunaris, 119. sphaericus, 99, 119. ephaerocephalus, Schloth. (an indeterminable fragment.) spinulosus, 68. Sternbcrgii, 71, 116. Siilzeri, 73. Tessini, 67. Tristani, 80. truncatus, 70. tuberculatus, 82. ungula, 75. variolaris, 114. velatus, 99. verticalis, 100. Zippii, 73. Trimerus, Green, 85. delpbinocepbalus, 86. Jacksonii, 112. Trimervs, platypleurus, 112. TEtNUCLEUs, Green, 56. Bigsbyi, 58. Caractaci, 56. ellipticus, 89. fimbriatus, 57. gibbosus, 63. granidatus, .')7. intermedius, 118. Isevis, 89. Lloydii, 57. Nillsoni, 118. nudus, 57. omatus, 58. otarion, 58. radiatus, 58. tessellatus, 58. Zethus, 79 verrucosus, 80, 82. uniplieatus, 82. ERRATA. Page 5, 11 lines from bottom, /oc Torrnbia, reud Torrubia. 17, note, for Triarthrus Breki, read Triarthus Bcckii. In the table, p. 34, for Crophyropoda read Lophyropoda ; and for Arthrostaca, read Arthrostraca, also in note to p. 35. C. AND J. ADLARD, PRINTERS, BARTHOLOMEW CLOSE. 4 ^^>, J- } 10. 11 a. «J^V %1 m Tai-. 11. 12. ■v^' 10. r,.i III ?^.t)"' / .J^ d.w. .Iivjcrfr rirl.rt sc. Taf.\'. Tili; \i -^^ \^-i > \\-- ^' '1%,. 4 A ^^;^- tt#-- M m PREPARING FOR PUBLICATION, BY SUBSCRIPTION, BIRKENHEAD SHORE: AN ATTEMPT TO COMMUNICATE GENERAL PRINCIPLES OF ZOOLOGY, Tiiiioniii Tin-; medii'.m ok A LOCAL FAUNA. Comprising, in an Octavo Volume {Price £1 1 0) I. 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