ROOM III. FOSSIL BATRACHIANS. 183 



first dorsal vertebra and the origin of the tail, and ten 

 ranged longitudinally. It equalled in size the species above 

 described. 



MYSTRIOSAURUS EGERTONL (On the top of Wall-case B.) 



The specimen thus labelled is the cast of a Teleosaurus, about 

 four feet in length, the original of which was obtained from 

 the Lias, at Altdorf. The cranium and elongated mandibles, 

 the skeleton of the trunk, and the bones of the four limbs, are 

 well displayed : there are many dermal scutes dispersed over 

 the trunk. 



The abundance of the fossil remains of this group of 

 amphibious loricated reptiles throughout the Liassic and 

 Oolitic formations, shows how numerous must have been 

 these carnivorous saurians in the marshes, deltas, and estuaries 

 of the islands and continents of those remote ages ; doubtless 

 the Teleosauri, like the Gavials of India, swarmed in the rivers 

 and lakes, and preyed on fishes and on the feebler tribes of 

 reptiles that inhabited the waters. 



FOSSIL BATRACHIANS. The reptiles termed Batrachians are 

 characterised by the transformation which they undergo in 

 the progress of development from the young to the adult 

 state ; the Frog, Toad, and Newt, are familiar examples of 

 this order. Their organs of aerial respiration consist of a pair 

 of lungs ; but in youth they are provided with gills, supported 

 as in fishes, by cartilaginous arches. These organs disappear 

 in most species, when the animals arrive at maturity ; but in 

 a few genera, as the Siren and Proteus, they are persistent. 

 The skeletons of these reptiles present corresponding modifi- 

 cations. The skull is, for the most part, much depressed, and 

 the cerebral cavity small ; it is united to the vertebral column 

 by two distinct condyles, situated on the sides of the occipital 

 or cranio-spinal aperture. The vertebral column, which in 

 some genera (as for example, in the frog) is very short, and 

 reduced to eight or ten bones, is composed in the higher 

 organised Batrachians of concavo-convex vertebrae, as in the 

 Crocodile ; but in the lower types, as the Siren, Proteus, and 

 Axolotl, the vertebrae are biconcave, as in numerous fossil 

 saurians. The ribs are rudimentary ; a condition which has 

 relation to the mode of reproduction in these animals. Some 

 of the Batrachians are edentulous, like the Turtles, but others 

 have numerous small, conical, uniform, closely-arranged teeth, 



