Ventriculites.[223] _Lign. 80, 81, 82._--At every step of our review of the fossil zoophytes, I find myself embarrassed by the conflicting opinions entertained by naturalists, respecting some of the most abundant of the extinct forms; arising from the imperfect state of our knowledge as to the structure of the originals, which compels a comparison with recent types, from which, perhaps, the fossils differed essentially in their organization. This remark especially applies to the zoophytes which have given rise to the fungiform flints so well known to the inhabitants of the chalk districts of Sussex, as "_petrified mushrooms_," from their close resemblance in form to fungi: a specimen with this name inscribed on it in the cabinet of a friend first drew my attention to these curious fossils. In _Lign. 80, figs. 2, 3, 4, 6, 7, 8, 9_, several flints of this kind are represented; _figs._ 3, 6, 8, are fungiform; _fig._ 7, is the upper part of a specimen, the stem having been broken off; _figs._ 2 and 4, are examples of the lower part of the zoophyte; in all, there are openings at the base, and a groove on the margin or edge of the upper part in which the structure of the inclosed fossil is visible; upon breaking these flints, sections of a funnel-shaped body are exposed. [223] Ventriculite; from _ventriculus_, a ventricle or sac. [Illustration: Lign. 80. Flints, deriving their forms from Zoophytes. _From the South Downs, near Lewes_; 1/6 _nat._ Fig. 1.--Choanites (?) Turbinatus. 2, 3, 4, 6, 7, 8, 9.--Flints, whose forms are derived from Ventriculites, provincially called "_petrified mushrooms_." 5.--Spongites labyrinthicus. 10.--Spongites flexuosus. ] The origin of these fossils will be understood by reference to the four specimens delineated in _Lign. 81_. In _fig._ 3, a fungiform flint, resembling _fig._ 6, of _Lign. 80_, is seen in the lower part of a cup-shaped zoophyte; while above, and surrounding the flint, the impression remains of the reticulated outer surface, deeply coloured by a ferruginous tinge. In _fig._ 4, _Lign. 81_, a small turbinated flint, resembling _fig._ 4, of _Lign. 80_, occupies the base, and three rootlets are seen emerging from it at a. In _Lign. 82, fig. 1_, in which the chalk has been removed so as to expose the outer surface of the Ventriculite, a flint occupies the centre at c; above which, the radiating reticulated structure is spread out on the chalk, _a_; the base, with its roots, is shown at _b_. [Illustration: Lign. 81. Ventriculites radiatus; 1/6 _nat._ _Chalk; near Lewes._ Fig. 1.--A perfect specimen in chalk, inverted, showing the external reticulated surface; the apex of the base projects in the centre. 2.--Specimen expanded, displaying the inner surface, studded over with the openings of the cells or tubes. 3.--A Ventriculite in chalk; the lower part inclosed in flint.