Ringueberg, E. N. S.

1886.--A trilobite track ill.u.s.trating one mode of progression of the trilobites. Proc. Amer. a.s.soc. Adv. Sci., vol. 35, p. 228 (abstract only).

Ruedemann, R.

1916.--The presence of a median eye in trilobites. Bull. New York State Mus., No. 189. pp. 127-143, pls. 34-36.

Schlotheim, E. F. von.

1823.--Nachtrage zur Petrefactenkunde, II. Gotha.

Six, Achille.

1884.--Les appendices des trilobites d'apres M. Ch. D. Walcott. Ann.

Soc. Geol. du Nord, vol. 11, pp. 228-236.

Spencer, W. K.

1903.--The hypostomic eyes of trilobites. Geol. Mag., dec. 4, vol. 10, pp. 489-492.

Staff, Hans v., and Reck, Hans.

1911.--Ueber die Lebensweise der Trilobiten. Eine entwicklungsmechanische Studie. Gesell. naturforsch. Freunde, Sitzb., pp. 130-146, figs. 1-20.

Sternberg, K. M.

1830.--Ueber die Gliederung und die Fusse der Trilobiten. Isis (Encycl. Zeitung), Oken, p. 516, pl. 5, figs. 1-3.

Stokes, C.

1823.--On a trilobite from Lake Huron. Trans. Geol. Soc., London, ser.

2, vol. 1, p. 208, pl. 27.

Swinnerton, H. H.

1919.--The facial suture of the trilobite. Geol. Mag., dec. 6, vol. 6, pp. 103-110.

Tornquist, S. L.

1896 A.--On the appendages of trilobites. Ibid., dec. 4, vol. 3, p. 142.

1896 B.--Linnaeus on the appendages of trilobites. Ibid., pp. 567-569.

Tothill, J. D.

1916.--The ancestry of insects, with particular reference to chilopods and trilobites. Amer. Jour. Sci. (4), vol. 42, pp. 373-383. text figs. 1-8.

Troedsson, G. T.

1918.--Om skanes Brachiopodskiffer. Lunds Universitets Arsskrift, n.

f., Avd. 2, Bd. 15, Nr. 3. pp. 57-67, pl. 1, figs. 19-24.

Valiant, W. S.

1901.--Appendaged trilobites. The Mineral Collector, vol. 8, No. 7, pp. 105-112.

Volborth, A. von.

1858.--Ueber die Bewegungs-Organe der Trilobiten. Verhandl. russ. k.

mineral. Gesell. zu St Petersburg, 1857-1858, p. 168.

1863.--Ueber die mit glatten Rumpfgliedern versehenen russischen Trilobiten, nebst einem Anhange ueber die Bewegungs-organe und ueber das Herz derselben. Mem. Acad. Imp. Sci. St. Petersburg, ser. 7, vol. 6, No. 2, pp. 44-47, pl. 1, fig. 12.

1866.--Ueber Herrn von Eichwald's Beitrag zu naheren Kenntniss der Illaenen. Bull. Soc. Imp. des Natural, de Moscou, vol. 39, p. 40.

Wahlenberg, G.

1821.--Petrificata telluris Suecana examinata a Georgio Wahlenberg.

Nova Acta Reg. Soc. Scient. Upsala, vol. 8.

Walcott, C. D.

1875.--Description of the interior surface of the dorsal sh.e.l.l of _Ceraurus pleurexanthemus_ Green. Ann. Lye. Nat. Hist. New York, vol. II, pp. 159-162, pl. 11.

1876.--Preliminary notice of the discovery of the natatory and branchial appendages of trilobites. 28th Rept. New York State Mus. Nat. Hist., adv. sheets, pp. 89-92; published as full report in 1879.

1877.--Notes on some sections of trilobites. 31st Rept. New York State Mus. Nat. Hist., adv. sheets, pp. 61-63, pl. 1; published as full report in 1879. Reviewed by Dames, Neues Jahrb. f. Min., Geol., u. Pal., Bd. 1, 1880, p. 428.

1879.--Notes upon the legs of trilobites. 31st Rept. New York State Mus. Nat. Hist., adv. sheets, p. 64.

1881.--The trilobite: New and old evidence relating to its organization. Bull. Mus. Comp. Zool., vol. 8, pp. 192-224, pls. 1-6.

1884.--The appendages of the trilobite. Science, vol. 3, pp. 276-279, figs. 1-3. Reviewed by Dames, Neues Jahrb. f. Min., Geol., u.