Cf. W. E. Ritter, Bull. Mus. Harvard, xxiv. 1893, p. 51.
For a good figure from life of Periophthalmus koelreuteri and an account of its habits, cf. S. J. Hickson, A Naturalist in North Celebes (London, 1889).
For the theories on the formation of the disk, cf. R. Storms, Ann. Mag. Nat. Hist. (6), ii. 1888, p. 67.
Cf. Holmwood, Proc. Zool. Soc. 1884, p. 411.
This character suffers one exception, to be found in Comephorus, a degraded form otherwise closely related to Cottocomephorus, in which the skeleton is typical of the present division.