BY PROFESSOR STEPHENS, M.A., F.G.S. 1189 



now, are liable from time to time to an invasion of flood waters 

 from the main channel. And we are, perhaps, not presuming too 

 much on these analogies when we conjecture that such shoals of 

 fish, thriving in the tepid waters of these lowland lagoons and 

 anabranches, and associated with Labyrinthodonts in these 

 habitats, may frequently have been killed in large numbers by a 

 sudden irruption of cold, perhaps icy, waters and mud which at 

 once destroyed and preserved them. It may be observed that the 

 Dipnoi, Protopterus, Lepidosiren and Ceratodus which claim some 

 sort of relationship to these amphibia, all belong to warm climates 

 and tepid waters ; and that the only Ganoids now existing 

 belong either to temperate and sub-tropical regions, like Lepi- 

 dosteus, or to tropical and sub-tropical, like Polypterus ; facts 

 which seem to indicate an adaptation, at least, to such conditions 

 as those under which our Triassic rocks were formed. I suppose 

 also that the strong head and throat-plates of the Labyrinthodonts, 

 as well as their hard dermal scutes or indurated integument, like 

 the ganoid scales of Paheoniscus, Lepidosteits, &c, the cuirass of 

 PUrichtltys and Coccosteus, (1) the bucklers of Acipe?iser, and the 

 rugged mail of the Crocodiles, bear all of them a certain relation 

 or accommodation to fluviatile habitats. These animals all live, 

 or appear to have lived, in great rivers with strong and irregular 

 currents, and subject to sudden inundation by freshes, in which 

 heavy materials, such as stones and logs, might be carried along 

 with a velocity dangerous to any organism upon which they might 

 strike. Some protection was manifestly requisite for the welfare 

 of aquatic animals exposed to such perils, and it was obviously 

 desirable, in their interests, that this protection should be such that 

 external hardness and stiffness should be accompanied by internal 

 elasticity and toughness, and that brittleness of any structure 

 should especially be avoided. All these conditions are united for 

 Labyrinthodonts in the deeply corrugated or pitted plates ot bone 

 and the hard scutes or studs which lay immediately beneath the 



(1) I assume that the conditions under which the Old Red and the New 

 Red Sandstone were deposited to have been closely analogous, if not 

 identical in character. 



