It appears to be still generally supposed that the Ichthyosaurians differed from all modern reptiles in having a short intestine with a spiral valve, like that of the more generalized fishes; and the supposition is rendered all the more plausible by the common belief that some at least of the Labyrinthodonts were similarly characterized. In each case, it is true, coprolites or masses of partially digested food, marked with the line of an intestinal spiral valve, are often found in the same strata as the skeletons; but, so far as I have been able to discover, no instance is known in which the spirally-marked coprolite actually occurs in its natural position in the fossilized animal.