224 Dr Hiszert on the Limestone of Burdiehouse 
which was afterwards extended to those of the herring and sal- 
mon, the importance of entomostraca, as an object of the food of 
many fish, was either unknown or lost sight of; and the po- 
pular opinion regarding the vendace of Lochmaben, long enter- 
tained, was, that, “ cameleon like,” they derived support from the 
medium in which they existed. But Dr Knox shewed that 
more solid matter was demanded for the food of these fish, and 
that the microscopic entomostraca diffused through the waters of 
Lochmaben served as the food of the vendace, affording them a 
rich, and, at the same time, a most delicate bait, for which they 
refused every other kind of food, and, consequently, were not to 
be captured by the line. 
In judging, then, from analogy, it is not an unreasonable sup- 
position, that the abundance of microscopic animals contained in 
the calcareous deposit of Burdiehouse might, like the modern 
Entomostraca of Lochmaben, have stood in a similar relation to 
certain of the smaller fossil fish which have been described, in 
having afforded them the abundant means of sustenance. 
But if this analogy may reasonably explain the kind of sup- 
port afforded to some of the smaller fish, it fails of application 
when we come to larger kinds. 
In proportion as coprolites increase in size, we find that they 
contain the scales of fish, shewing that the larger fish to which 
these foecal remains are referred, must have frequented the ancient 
river or lake, indicated by the limestone of Burdiehouse, in quest 
of their prey. Many of the indigested scales are of smaller fish, 
but in some of them I have found larger scales, as well as frag- 
ments of larger bones, shewing that the Megalichthys might have 
even lived upon its own progeny: 
But, as a contemporaneous fish of extraordinary magnitude, 
the Gyracanthus formosus, must have likewise frequented these 
ancient waters, it is not always easy to make very accurate copro- 
litic distinctions. 
7 
