the spinal marrow , &c, of the Proteosaurus. 161 
bodies of these vertebrae, when met with without the spinous 
processes, have so close a resemblance to the vertebrae of 
the shark in a fossil state, that they have till now been mis- 
taken for them ; and I found several of them preserved in 
the Hunterian Collection, marked as belonging to that 
fish. 
The particular structure which I have endeavoured to 
describe, will be more readily understood by a reference to 
the annexed Plate, (PI. XV.) in which it is very accurately 
represented. 
In the same figure in which the manner of setting on the 
spinous process to the vertebra is shown, there is (what I 
have never before met with), one of the feet paddles or fins, 
(for it is difficult to say which of these names is the most 
proper), in which the bones are nearly complete ; for although 
some of the smallest are wanting, there are quite enough to 
give a tolerably exact figure of the outline ; of this no other 
specimen has afforded the most distant idea. This outline 
certainly has more resemblance to that of a fin, than to any 
of the fore feet of the tribe of lacerta, or the seal, or even the 
turtle ; and, what is the most remarkable circumstance, there 
is nothing in any way correspondent to the thumb, or claw 
for laying hold, which distinguishes the animals that occa- 
sionally inhabit the sea, and come ashore for the purpose of 
laying their eggs, or depositing their young. It certainly 
has the appearance of a fin ; but if in future it is to be de- 
signated under that name, it is always to be understood that 
this fin, contrary to every thing hitherto known in nature, is 
made up of bony materials ; and it is from the great number 
of bones of which it is composed, and the correspondent 
