210 GEOLOGICAL DISTRIBUTION 



smaller teeth of the same kind. The external form of all 

 these teeth are nearly conical, and within them is a conical 

 cavity, like that within the teeth of many Saurians ; 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 entirely with 

 that of the teeth of the living Lepidosteus osseus. (PI. 27*, 

 Figs. 1, 2, 3.) 



Smaller Sauroid Fishes only have been noticed in the 



* We owe the discovery of tiiese vsry curious teetli, 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 Coprolites, derived apparently from predaceous Fishes. It is 

 abundantly charged also with ferns, and other plants of the coal formation; 

 and with the crustaceous remains of Cypris, a genus known only as an in- 

 habitant of fresh-water. These circumstances, and the absence of Corals 

 and Encrinites, and of all species of marine shells, render it probable that this 

 deposite was formed in a fresh-water lake, or estuary. It has been recog- 

 nised in various and distant places, at the bottom of the carboniferous strata 

 near Edinburgh. 



In the Transactions of the Royal Society of Edinburgh, Vol. XIII. Dr. Hib- 

 bert has published a most interesting description of the recent discoveries 

 made in the limestone of Burdie House, illustrated with engravings, from 

 which the larger teeth in our plate are copied. (Pi. 27, Fig. 11, 12, 13, 14.) 

 The smaller figures, PI. 27, Fig, 9, and Pi. 27», Fig. 4, are drawn from spe- 

 cimens belonging to Dr. Hibbert and the Royal Society of Edinburgh. 



In this memoir, Dr. Hibbert has also published figures of some curious 

 large scales, found at Burdie House, with the teeth of Megalichthys, and re- 

 ferred by M. Agassiz to that Fish. Similar scales have been noticed in 

 various parts of the Edinburgh Coal field, and also in the Coal formation of 

 Newcastle-on-Tyne. Unique specimens of the heads of two similar Fishes, 

 and part of a body covered with scales, from the Coal field near Leeds, are 

 preserved in the museum of that tovyn. 



Sir Philip Grey Egerton has recently discovered scales of the Megalich- 

 thys, with teeth and bones of some other Fishes, and also Coprolites, in the 

 Coal formation of Silverdale, and Newcastle-undcf-Line. These occur in 

 a stratum of shale, containing siiells of three species of Unio, with balls of 

 irgillaceous iron ore and plants,^ 



