1899.--O some new myriopods from the Palæozoic rocks of Scotland. Ibid., vol. 14, pp. 113-126, pl. 4. Quenstedt, A. 1837.--Beitrag zur Kenntniss der Trilobiten, mit besonderer Rücksicht auf ihre bestimmte Gliederzahl. Archiv f. Naturg., Berlin, 3. Jahrg., 1 Bd., pp. 337-352. Raymond, P. E. 1910.--On two new trilobites from the Chazy near Ottawa, Ontario. Ottawa Nat., vol. 24, pp. 129-134, pl. 2. 1917.--Beecher's classification of trilobites, after twenty years. Amer. Jour. Sci. (4), vol. 43, pp. 196-210, text figs. 1-3. Raymond, P. E., and Barton, D. C. 1913.--A revision of the American species of _Ceraurus_. Bull. Mus. Comp. Zool., vol. 54, pp. 525-543. pls. 1, 2, 3 text figs. 1-3. Reed, F. R. C. 1916.--The genus _Trinucleus_. Pt. 4. Geol. Mag., dec. 6, vol. 3, pp. 121, 122. Richter, R. 1848.--Bitrag zur Palæeontologie des Thüringer Waldes. Dresden and Leipzig. Ringueberg, E. N. S. 1886.--A trilobite track illustrating one mode of progression of the trilobites. Proc. Amer. Assoc. 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.--Nachträge zur Petrefactenkunde, II. Gotha. Six, Achille. 1884.--Les appendices des trilobites d'après 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 Füsse 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. Törnquist, S. L. 1896 A.--On the appendages of trilobites. Ibid., dec. 4, vol. 3, p. 142. 1896 B.--Linnæus 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.