of the Flints of the Upper Chalk. 5 



by 4_, unbroken, and of most fantastic form. Another, about 

 4 inches by 3, and containing one Ventriculite which it just 

 encases, presents two beautiful Dianchoras and at least eight 

 Ostreas, besides many small shells. These are lying on the ex- 

 ternal surface, just sunk, as it were, in the flint, as they would 

 sink in water, but not at all covered*. No hollow of a sponge 

 could have retained them thus. 



I have seen, in Mr. Bowerbank's valuable collection of sponges, 

 a specimen in which one small shell is imbedded : this may have 

 happened in casual instances with small dead shells, but where 

 can it be found, in recent sponges, from the most favourable spots, 

 that they are full, as we find the flints full, of bivalves large, nu- 

 merous and perfect, and apparently living when enveloped ? 



It is assumed by this theory that the sponges grew over the 

 shells and other organic objects whicb lay on the surface of the 

 mud. But the observed facts are wholly at variance with this 

 assumption. The organic bodies are found, not on the under 

 surface of the flints only, but equally on all parts of the surface 

 and in all parts of the inside. Now how can this be accounted 

 for ? Shall we suppose that the shells, &c. sank down from 

 above and rested on the sponges till grown over, unafifected by 

 their natural tendency to fall to the actual bottom on the slightest 

 motion in the water ? What follows then ? necessarily tbis : that 

 the upper surfaces of the tabular masses would, far more than 

 any other flints, display these remains, as such shells, &c. would 

 be far less liable to roll ofi" the assumed sponges of this form. 

 But do the facts support this necessary conclusion from the sponge 

 theory ? Assuredly not. It is the nodular flints in which are 

 found most of the organic remains of the class alluded to. Thus 

 on the flat surfaces, ofi" whicb shells, &c. could not fall, they are 

 not found in any abundance, while on the smaller and nodular 

 masses, of all sizes, ofi^ which the least motion, if not their natural 

 gravity, would cause them to fall, they are found in great abun- 

 dance ! The same result follows from the observation of the fact, 

 that on the under side of the upper part of the goblet-shaped flints 

 which inclose Ventriculites (and the upper and under surfaces of 

 which can therefore be positively known), shells and other re- 

 mains, not originally affixed to the surface of the animal, are found, 

 which therefore could never have been either lying on the ground 

 or have fallen from above. These two sets of facts are equally 

 conclusive against the sponge enveloping theory. 



The Echinites alone, extensively examined, afford conclusive 

 evidence against the sponge theory. These are very frequently 

 indeed found in the very centre of flints. They are sometimes 



* See note, p. 7, for explanation of this fact. 



