CHARACTER AND SIZE. 
275 
PI. 27, Figs. 11, 12, 13, 14, represent teeth of 
the largest Sauroid Fishes yet discovered, equal- 
ling in size the teeth of the largest Crocodiles : 
they occur in the lower region of the Coal form- 
ation near Edinburgh, and are referred by M. 
Agassiz to a new genus, Megalicthys. PI. 27, 
Fig. 9, and PI. 27% Fig. 4, are fragments of 
jaws, containing many smaller teeth of the same 
kind. The external form of all these teeth is 
nearly conical, and within them is a conical 
cavity, like that within the teeth of many Sau- 
rians ; their base is fluted, like the base of the 
teeth of the Ichthyosaurus. Their prodigious 
size shows the magnitude which Fishes of this 
family attained at a period so early as that of 
the Coal formation their structure coincides 
* We owe the discovery of these very curious teeth, and much 
valuable information on the Geology of the neighbourhood of 
Edinburgh, to the zeal and discernment of Dr. Hibbert, in the 
spring of 1834. The limestone in which these Fishes occur lies 
near the bottom of the Coal formation, and is loaded with Copro- 
lites, derived apparently from predaceous Fishes. It is abun- 
dantly charged also with ferns, and other plants of the coal 
formation ; and with the crustaceous remains of Cypris, a genus 
tnown only as an inhabitant of fresh water. These circum- 
stances, and the absence of Corals and Encrinites, and of all 
species of marine shells, render it probable that this deposit was 
formed in a freshwater lake, or estuary. It has been recog- 
nized in various and distant places, at the bottom of the car- 
boniferous strata near Edinburgh. 
In the Transactions of the Royal Society of Edinburgh, Vol. 
XIII. Dr. Hibbert has published a most interesting description of 
fbe recent discoveries made in the limestone of Burdie House, 
