[27]

Von Stummer-Traunfels, Zeitschr. f. wiss. Zool. Bd. lx. 1895, p. 689.

[28]

Planocera pellucida Mertens, P. simrothi v. Grff., P. grubei Grff., Stylochoplana sargassicola Mertens, S. californica Woodworth, Planctoplana challengeri Grff., all belonging to the Planoceridae. See v. Graff, "Pelagische Polycladen," Zeitschrift f. wiss. Zoologie, Bd. lv. 1892, p. 190.

[29]

Cambridge Natural History, vol. iii. p. 74.

[30]

Lang, "Polycladen," p. 629.

[31]

Wheeler, Journal of Morphology, vol. ix. part 2, 1894, p. 195.