188 INTESTINAL STRUCTURE OF ICHTHYOSAURUS. 
discovery of Coprolites, (see PI. 15,) i. e. of foecal 
remains in a state of petrifaction, dispersed 
through the same strata in which these skeletons 
are buried. The state of preservation of these 
very curious petrified bodies is often so perfect, 
as to indicate not only the food of the animals 
from which they were derived, but also the 
dimensions, form, and structure of their stomach, 
and intestinal canal.* 
On the shore at Lyme Regis, these Coprolites 
are so abundant, that they lie in some parts of 
the lias like potatoes scattered in the ground ; still 
* The following description of tliese Coprolites, is given in 
my memoir on this subject, published in the Transactions of the 
Geological Society of London, 1829, (vol. iii. n. s. parti, p. 224. 
with three plates.) 
" In variety of size and external form, the Coprolites resemble 
oblong pebbles or kidney-potatoes. They, for the most part, 
vary from two to four inches in length, and from one to 
two inches in diameter. Some few are much larger, and bear 
a due proportion to the gigantic calibre of the largest Ichthyo- 
sauri ; others are small, and bear a similar ratio to the more 
infantine individuals of the same species, and to small fishes : 
some are flat and amorphous, as if the substance had been 
voided in a semifluid state ; others are flattened by pressure of 
the shale. Their usual colour is ash grey, sometimes inter- 
spersed with black, and sometimes wholly black. Their sub- 
stance is of a compact earthy texture, resembling indurated 
clay, and having a conchoidal and glossy fracture. The struc- 
ture of the Coprolites at Lyme Regis is in most cases tortuous, 
but the number of coils is very unequal ; the most common 
number is three : the greatest I have seen is six : these varia- 
tions may depend on the various species of animals from which 
they are derived ; I find analogous variations in the tortuous 
intestines of modern Skates, Sharks, and Dog-fish. Some 
