1860.--Lethaea Rossica, pl. 21.

1863.--Beitrage zur nahern Kenntniss der in meiner Lethaea Rossica beschriebenen Ilaenen. Bull. Soc. Imp. des Natural, de Moscou, vol. 36, p. 408.

Emmrich, H. F.

1839.--De trilobitis dissertatio petrefactologica, etc. Berlin.

Exner, S.

1891.--Die Physiologic der facettirten Augen von Krebsen und Insecten.

Leipzig and Vienna. Pp. 33-35, pl. 2, figs. 18-19.

Finch, G. E.

1904.--Notes on the position of the individuals in a group of _Nileus vigilans_ found at Elgin, Iowa. Proc. Iowa Acad. Sci. for 1903, vol. 11, pp. 179-181, pl. 14.

Gegenbaur, C.

1878.--Elements of comparative anatomy. Eng. ed. (Bell and Lankester).

London.

Goldfuss, A.

1828.--Observation sur le place qu'occupent les trilobites dans le regne animal. Ann. Sci. Nat., Zoologie, vol. 15, p. 83, pl. 2, figs. 5, 7, 9, 10.

Green, J.

1839 A.--The inferior surface of the trilobite discovered. The Friend, Philadelphia, March 16.

1839 B.--The inferior surface of the trilobite discovered.

Ill.u.s.trated, with colored models. Philadelphia.

1839 C.--Remarks on the trilobites. Amer. Jour. Sci. (1), vol. 37, p. 25 _et seq._

1840.--An additional fact, ill.u.s.trating the inferior surface of _Calymene bufo_. Ibid., vol. 38, p. 410.

Handlirsch, A.

1906.--Ueber Phylogenie der Arthropoden. Verhandl. d. k. k. zool.-bot.

Gesell., Vienna, Jahrg. 1906, pp. 88-103.

1907.--Functionswechsel einiger Organe bei Arthropoden. Ibid., Jahrg.

1907, pp. 153-158.

1908.--Die fossilen Insekten. Leipzig.

1914.--Eine interessante Crustaceenform aus der Trias der Vogesen.

Verhandl. d. k. k. zool.-bot. Gesell., Vienna, Jahrg. 1914, pp. 1-7, pls. 1, 2.

Hawle, I., and Corda, A. J. C.

1847.--Prodrom einer Monographie der boehmischen Trilobiten, pp. 9, 24, 56, pl. 2, fig. 10; pl. 3, fig. 15; pl. 4, fig. 33b-g.

Jaekel, O.

1901.--Beitrage zur Beurtheilung der Trilobiten, Theil I. Zeits. d.

deutsch. geol. Gesell., Bd. 53, pp. 133-171. Pis. 4-6, text figs. 1-30.

Kingsley, J. S.

1897.--The systematic position of the trilobites. Amer. Geol., vol. 20, pp. 33-38.

Koenen, A. von.

1872.--Ueber die Organisation der Trilobiten. Verhandl. d. naturhist.

Ver. d. preuss. Rheinl. u. Westphalen, vol. 29, C, pp. 93-95.

1880.--Ueber die Unterseite der Trilobiten. Neues Jahrb. f. Min.., Geol., u. Pal,, Bd. 1, pp. 430-432. pl. 8.

Lang, A.

1891.--Text-book of comparative anatomy, Eng. ed. (Bernard). London.

Lankester, E. R.

1881.--Observations and reflections on the appendages and on the nervous system of _Apus cancriformis_. Quart. Jour. Micros. Soc., vol. 21, pp. 343-376.

Laurie, M.

1911.--A reconstructed trilobite. Nature, vol. 88, p. 26.

Lindstroem, G.

1901.--Researches on the visual organs of the trilobites. K. svenska Vet.-Akad. Handl., new ser., vol. 34, pp. 1-86, pls. 1-6.