Gegenbaur, Grundzüge vergl. Anat. 2 ed. 1870, p. 158.
Lankester, Quart. J. Micr. Sci. xvii. 1877, p. 448 (= Aspidophora, Allman, J. Linn. Soc. xiv. 1879, pp. 490 n., 586).
Spengel, Zool. Jahrb. Syst. xv. 1902, p. 209.
Fauna u. Flora G.v. Neapel, 18 Monogr. 1893 (reviewed by MacBride in Quart. J. Micr. Sci. xxxvi. 1894, p. 385); Zool. Jahrb. Anat. xviii. Pt. ii. 1903, p. 271.
Quart. J. Micr. Sci. xxiv. 1884, p. 208; xxv. Suppl. 1885, p. 81; xxvi 1886, pp. 511, 535.