16 PRESIDENTS ADDRESS. 



less furnished with a protecting armour of bony plates. They 

 date from the Carboniferous Age. The body is elongated, and 

 furnished with a tail. The orbits have usually bony sclerotic 

 scales. They ranged in Europe from the Carboniferous to the 

 Permian Age, and were abundant, especially in the latter. Only 

 one genus survived to the Jurassic Age. The foot-prints of 

 Chdiotherium may possibly have belonged to one or more of 

 this family. The dental system of the Stegocephali was more for- 

 midable than in any other Batrachian, and differs in the implan- 

 tation of the teeth in distinct sockets and the development of the 

 anterior into large tusks. The teeth of the Labyrinthodonts have 

 a peculiar structure which suggested its name, on account of the 

 singular cerebriform convolutions pervading every portion. 

 The Batrachian characters of the Labyrinthodont foreshadow 

 and lead up to those of the Crocodile, the highest de- 

 veloped of the Reptilia, Both have a double occipital-condyle, 

 vertebrae biconcave, and branchial apertures, which are retained 

 some time after birth. Many have an exo-skeleton, which appears 

 to have been confined to the ventral part of the body. Reptiles 

 present a remarkable contrast to Birds and Fish with regard to 

 their inactivity and their power of sustaining a lengthened priva- 

 tion of food. The extinct Reptiles equally shared the characters 

 of Fish with those of the highly-specialised Reptiles now living. 

 Others on the other hand approximated to the Mammalian type. 

 The inferior organisation of the reptile is shown more distinctly 

 in the cranium than in any other part of the skeleton. The 

 occipital-bone of the Crocodile is composed of four pieces, which 

 remain distinct throughout life. With Mammalia they coalesce 

 and form one single element. The lower-jaw of Reptiles shows a 

 peculiarity to which there is no parallel in any other Order. 

 Each side is divided into five and sometimes six distinct pieces, 

 united by sutures, apparently to diminish the danger of fracture 

 to which those with long, slender jaws, such as the extinct 

 Tehosauria, are liable. Ichthyosauria, those great marine car- 

 nivorous Reptiles, were devoid of an exo-skcleton, the orbits 

 furnished with an ossified sclerotic-ring ; teeth implanted in a 



