[401] The classification is that of Foord, Catal. Fossil Cephal. Brit. Mus., 1888.
[402] Saville Kent, Proc. Roy. Soc. Queensland, vi. p. 229.
[403] J. Power, Ann. Mag. N. H. (2) xx. p. 334; P. Z. S. 1836, p. 113; Arch. Zool. Exp. Gén. (3) i. 1893, p. 105.
[404] In deference to Bergh’s high authority, the position of a sub-order is here given to the Ascoglossa. It may be doubted whether that position will stand the test of further investigation, and whether the families concerned will not be added to the Cladohepatic Nudibranchs.
[405] This family has also been classified with the Bulloidea and with the Aplysioidea.
[406] It appears more convenient to treat the whole group together, rather than deal with the two sections separately.
[407] An operculum is said to exist in the young forms of Auricula and Parmacella.
[408] Proc. Ac. Philad. 1892, p. 390.
[409] Compare Jackson, Amer. Nat. xxv. p. 11 f.
[410] “A Monograph of the British Fossil Brachiopoda,” Palaeontographical Society, London, vols. i.-v. 1851–84.