75 
to prove their animal nature. By the aid of a lens, of moderate power, 
the central depression and projection are very plainly seen : and the 
eye, thus assisted, also discovers numerous thread-like processes, by 
which these bodies are laterally connected. This curious conformation 
of these substances is still more distinctly observable, on the inferior 
surface of this stone, which displays its fracture ; it having been 
evidently here separated by violence from the mass to which it originally 
belonged. 
At Plate VIII. Fig. 12, is a magnified representation of five of these 
bodies, by which the frequent connexion effected by means of these 
filamentary processes will be distinctly seen. The bodies which are 
here figured are connected by lateral filaments ; but from the marks 
which remain of attachment of similar filaments, on their superior 
surfaces, it is highly probable that these bodies were connected by 
filaments, proceeding from several parts of their surface. Such an 
arrangement of parts seems decidedly to determine that these bodies are 
not, as might be supposed; merely calcareous concretions ; but that they 
have indubitably derived their existence from the regular operation of 
the laws of animal organization. 
The silicious pebble, Plate VIII. Fig. 10, which was found in the 
Gravel-pits, near Hackney, had long been the subject of fruitless 
conjecture: no circumstance being discoverable in its appearance which 
would determine its place in any classification, nor any analogous body 
being recollected by which its nature could be illustrated. By its 
comparison with the preceding specimen, its analogy with it appears to 
be indisputable. The whole fossil being of a calcedonic substance, 
possesses that degree of hardness which has rendered it but little 
susceptible of injury from mechanical violence ; and hence its peculiarity 
of structure is still distinctly observable. 
In this specimen, as well as in another, from the Leverian Collection, 
the character of the original substance is plainly discoverable. 
Small round compressed bodies, not exceeding an eighth of an inch 
