COPROLU’ES. 
191 
The preservation of such foecal matter, and its 
conversion to the state of stone, I’esult from the 
imperishable nature of the phosphate of lime, of 
which both bones, and the prodiicts of digested 
bones are equally composed. 
The skeleton of another Ichthyosaurus in the 
Oxford Museum, from the lias at Lyme Regis, 
(Rl. 14) shews a large mass of fish scales, chiefly 
referrible to the Pholidophorus limbatus,* in- 
termixt with coprolite throughout the entire 
region of the ribs ; this mass is overlaid by many 
ribs, and although, in some degree perhaps, 
extended by pressure, it shows that the length 
* According to Professor Agassiz, the scales of Pholidophorus 
f mbatus, a species very frequent among the fossils of the lias, are 
fnore abundant than those of any other fish in the Coprolites found 
"r that formation at Lyme Regis; and shew that this species was 
t'le i)rincipal food of these reptiles. In Coprolites from the coal 
formation, near Edinburgh, he has also recognised the scales 
ol PalsBoniscus, and of other fishes that are often found entire 
in strata that accompany the coal of that neighbourhood. 
Scales of the Zeus Lewisiensis, a fish discovered by Mr. Man- 
tell, in the chalk, occur in Coprolites derived from voracious 
fishes during the deposition of this formation. 
A Coprolite from the lias, (PI. 15, Fig. 3), remarkable for its 
spiral convolutions, and vascular impressions, afibrds a striking 
Sample of the minute accuracy with which investigations are 
t>w conducted by naturalists, and of the kind of evidence which 
^ tnparative anatomy contributes in aid of geological enquiry. 
^ It one side of this Coprolite, there is a small scale, (Fig. 3, a,) 
'' lie 1 1 could only refer to some unknown fish, of the numerous 
Species that occur in the lias. The instant I shewed it to M. 
gassiz, he not only pronounced its species to be the Pholido- 
P lorus limbatus ; but at once declared the precise place which 
IS scale had occupied upon the body of the fish. A minute 
