Choanites Königi, _Lign. 75._--The zoophyte which has given rise to the fossils I have distinguished by the name of Choanites,[213] is of a spheroidal or sub-ovate form, and appears to have been composed of a softer tissue than the ordinary sponges. It has a central cavity, and was fixed at the base by long rootlets: its mass is traversed by numerous tubes or channels, which open on the inner surface of the cavity; it differs from Siphonia in not having a stem composed of bundles of tubes, and probably also in its constituent substance. Among the Sussex and Wiltshire chalk-flints specimens of this zoophyte are very common; they are easily recognized by the peculiar markings produced by the silicified tubes that radiate from the centre, as seen in _Lign. 75, fig. 4_. The semi-diaphanous pebbles on the Sussex coast, more frequently contain Choanites than any other zoophytes. From the beautiful and varied markings observable in the polished sections, they are in great request for brooches, and are termed _petrified sea-animal flowers_[214] by the lapidaries; among the shingle on the sea-shore at Bognor, Worthing, and other places, very fine examples may be collected. [213] Foss. S. D. p. 178. [214] From the supposition that the original was an _Actinia_, or _Sea-Anemone_. A coloured vertical section of a pebble of this kind is figured in my "Thoughts on a Pebble," Eighth Edition, pl. ii. See coloured figures of Choanites in Pict. Atlas, pl. xlii. _fig._ 1, 9, and 10; pl. xliv. _fig._ 8; and pl. xlv. _fig._ 10. [Illustration: Lign. 75. Choanites Königi. (G. A. M.) _Chalk, Lewes._ Fig. 1.--Transverse section of a siliceous specimen. 2.--Upper portion of a _Choanite_, in chalk, showing the opening of the central cavity at _a_. 3.--Vertical section of a Choanite, in flint, exposing a section of the mass, and canals passing obliquely from the central cavity, through the substance. 4.--Choanite in flint; the usual appearance of these fossils. 5.--Various kinds of Spicula of fossil sponges; _magnified_. ]