A lobed zoophyte, resembling the above in its general form, and long rootlets, is distinguished by a large central cavity, which is continued above the body in the form of a cylinder.[203] [203] Beautiful figures of these and other chalk zoophytes are given by Mr. Toulmin Smith in his elegant memoir "On the Ventriculidæ." The specimens above described are named _Bracholites_ by Mr. Smith. The plan of the present work forbids the discussion of that author's opinions and inferences. Spongites (?) flexuosus. _Lign. 80, fig. 10._--Among the cyathiform flints that abound in the chalk, a very elegant species is distinguished by a flexuous band that runs round the margin, and indicates the lobed structure of the original. In the chalk of Flamborough Head, Yorkshire, many beautiful cyathiform sponges are preserved, in which the outer surface is thickly covered with projecting hollow papillæ; these fossils are generally silicified, the surface and pores being frosted over with minute quartz crystals. The museum of the York Institution contains a splendid series of these spongites.[204] [204] The silicified state of these zoophytes was first detected by Mr. Charlesworth, who by immersing specimens in dilate hydrochloric acid, obtained admirable examples of the delicate structure of the original. [Sidenote: FOSSIL ZOOPHYTES OF FARINGDON.] Fossil Zoophytes of Faringdon. _Lign. 70, 71, 72._--The richest locality for fossil sponges in England is in the immediate neighbourhood of the little town of Faringdon, in Berkshire.[205] The Greensand beds that overlie the Oolite in that district, consist of a coarse friable aggregation of sand, comminuted shells, corals, amorphozoa, and echinoderms, more or less consolidated by a ferruginous cement. The gravel-pits, as the quarries are locally termed, expose what evidently were banks of detritus thrown up on the strand of a sea-margin; among the water-worn and fragmentary relics of oolitic as well as cretaceous forms, many perfect sponges of various kinds may be collected in the course of a few hours. Figures of some of the common species are subjoined. [205] See Excursions, in vol. ii. [Illustration: Lign. 70. Fossil Zoophytes. Fig. 1.--Lunulites radiatus. _Preston Chalk-pits_; view of the convex side. (_Mr. Walter Mantell._) 1_a_.--Front view; _nat._ 1_b_.--Portion of the surface of fig. 1, magnified. 2.--Scyphia intermedia; 1/2 _nat._ _Faringdon._ 3.--Lithododendron sociale: the left-hand branch shows a vertical section at the upper part, displaying the internal structure; 1/2 _nat._ _Mountain Limestone, Yorkshire._ 4.--Verticillipora anastomosans. _Faringdon._ 5.--Scyphia ramosa; 1/2 _nat._ _Faringdon._ 6.--Scyphia foraminosa; 1/2 _nat._ _Faringdon._ 7.--Cnemidium astrophorum; 1/3 _nat._ _Faringdon._ ]