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 näheren Kenntniss der Illænen. 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 shell 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. Pal.., Bd. 1, 1885, Referate, p. 102. 1894.--Note of some appendages of the trilobites. Proc. Biol. Soc. Washington, vol. 9, pp. 89-97, pl. 1; Geol. Mag., dec. 4, vol. 1, pp. 246-251, pl. 8. 1911.--Middle Cambrian Merostomata. Smithson. Misc. Coll., vol. 57, No. 2, pp. 17-40, pls. 2-7. 1912 A.--Middle Cambrian Branchiopoda, Malacostraca, Trilobita, and Merostomata. Ibid., No. 6, pp. 145-228, pls. 24-34, text figs. 8-10. 1912 B.--New York Potsdam-Hoyt fauna. Ibid., No. 9, pp. 251-304, pls. 37-49. 1913.--Eastman-Zittel Text-book of Paleontology, ed. 2, vol. 1, figs. 1343, 1376, 1377. 1916.--Ann Rept., Secretary Smithsonian Inst, for 1915, pl. 9. 1918.--Appendages of trilobites. Smithsonian Misc. Coll., vol. 67, No. 4, pp. 115-226, pls. 14-42. Watase, S. 1890.--On the morphology of the compound eyes of arthropods. Johns Hopkins Univ., Studies from Biol. Lab., vol. 4, no. 6, p. 290 (footnote). Woodward, H. 1870.--Note on the palpus and other appendages of _Asaphus_, from the Trenton limestone, in the British Museum. Quart. Jour. Geol. Soc., London, vol. 26, pp. 486-488, fig. 1. Abstract in Geol. Mag., dec. 1, vol. 7, p. 292, also in Nature, vol. 2, p. 94.