• of the Flints of the Upper Chalk. 207 



swerecl. On page 3 of my paper is discussed the necessarily im- 

 plied joecw/2«r and 5jom«/ affinity of sponges for liquid silex; on the 

 same and following pages, the sparing and fragmentary presence 

 and character of the remains of tissue; on the latter page, the non- 

 existence of any places of roots, and the contrary fact of un- 

 doubted sponges being found in which such places are always 

 present. On page 5, not only is the abundance and size of shells^ 

 &c. found within flints noticed, but the position of the organic 

 bodies found on the exterior of flints is very fully and promi- 

 nently discussed. On page 6 the condition of certain zoophytes 

 is noticed. On page 7, the important fact that — and it is explained 

 why — shells fixed on Ventriculites are left bare by the flint, and the 

 fact that soft animal matter, and not, as in recent sponges, shells 

 and other hard substances, formed the point of attraction for the 

 flint. On page 8 the phsenomena of Ventriculites are more fully 

 noticed. On page 9, the important fact of flint occurring to the 

 same extent without as within the Ventriculite, though with no 

 connexion between them ; and, on the same page, the extremely 

 frequent case of flint nodules being found round the roots of 

 Ventriculites, where sponges could never reach, but which places 

 would be peculiarly apt, according to my view of the formation 

 of the flints, to exhibit these aggregations. 



The non-sponge character of Ventriculites is also shown on 

 page 9*, and also certain inconceivable phsenomena which the 

 sponge theory requires (among many others) to explain the sili- 

 cification of Ventriculites. 



The true nature and character of the specimens figured is 

 described on page 10, &c., and the mode of their formation en- 

 deavoured to be explained in detail ; and it is proved that the 

 liquid silex could not possibly have been in a gelatinous state, 

 but must, on the contrary, have been in a state of extreme 

 liquidity, and liable to very rapid solidification ; which rapidity 

 of solidification is shown to be necessarily inconsistent with the 

 sponge theory, and which Mr. Bowerbank^s remark (page 250), 

 on the very enduring character of the horny skeleton of sponges, 

 makes still more evident. 



On pages 15 and 16, the modes and forms assumed by the 

 flint nodules t and tabular masses, and the imbedment in them 

 of the various classes of organic remains, are explained, the pre- 

 sence of the fragmentary tissue having been before explained on 

 page 4. 



* Mr. Bowerbank's alleged recent Ventriculites (p. 258) have no analogy 

 whatever to the true Ventriculites ; nor are his specimens so new or rare as 

 he imagines, the most striking of them being beautifully figured, with others 

 no less striking, on plate 59 of Ellis's Zoophytes. 



t See note 'post, p. 308. 



