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this surface. The whole appearance of this fossil very much resembles 
that of a leech or slug in a contracted state. 
From these bodies having been found regularly disposed together, 
and particularly from one instance mentioned by Mr. Walcot, in which 
twenty-five of these oblong bodies were regularly placed in four rows, 
there can be no doubt that they are not single palates ; but that many 
of them, regularly disposed, constituted the platform of the palate of 
some unknown fish. 
The palate of another species of unknown fish appears to have been 
formed by the regular arrangement of quadrangular bodies, a beautiful 
specimen of one of which is figured Plate XIX. Fig. 18. The hard 
part of these bodies, corresponding to the enamel of teeth, is disposed, 
on the middle part of the upper surface, in sharp and slightly-curved 
ridges, alternating with corresponding depressions. These are sur- 
rounded by a border, formed of obtuse papillae and rugae, disposed in 
a very confused and irregular manner. In some specimens, this border 
is not present. These palates are chiefly found among the chalk of Kent 
and Surrey. The most interesting fossil of this description, which I 
possess, is one which is embedded in the centre of a nodule of flint. 
The fossil, Plate XVIII. Fig. 12, is one of the component parts of the 
roof of the mouth of some other unknown fish. It resembles the preced- 
ing fossil in the disposition of its ridges, &c. but differs from it in having 
a much greater convexity, being full as high as it is long. It is found, 
though much more rarely than the former, in masses of chalk, and 
most frequently in the neighbourhood of Devizes, in Wiltshire. 
Several of this, and of the two preceding species of fossil palates, 
were exposed to the action of dilute muriatic acid : when the existence 
of their membranous laminae was evinced by numerous delicate Jlocculi 
becoming partly detached from the surface. In the leech-like palate, 
the phenomena which occurred were very interesting. After the fossil 
had been exposed about twelve hours to the action of the acid, its dark 
surface gradually disappeared, and was succeeded by one of a silvery 
