THE PRESIDENT'S ADDRESS. 151 



structure that we are acquainted with among the vertebrata. Three 

 distinct groups are here found — the Enaliosaurians, or marine reptiles, 

 the PtcrodactyUans, or aerial reptiles, and the Teleosaurian, or land and 

 river reptiles. 



Among the Enaliosaurians, the Ichthyosaurus will always stand 

 supreme. This marvellous animal had the skull of a crocodile, the 

 eye fashioned like a bird and a turtle. It had the backbone of a fish, 

 the paddles of a whale, and the scapular arch of a Platypus. 



The Plesiosarus was distinguished by its long neck resembling that of 

 a swan united to the trunk of a quadruped, with ribs like a chameleon. 

 The structure of these Enaliosaurians may be pointed out as specialised 

 examples of ancient osteology which had no ancestors in the Trias, and 

 no descendant beyond the Jurassic age. 



There is yet another reptile that appeared for the first time in the 

 Lias, which has indeed a unique history, seeing tbat nothing approach- 

 ing to it is found either in living or extinct natural forms. This is 

 the Pterodactyle, a flying reptile whose skeleton was modified and 

 adapted to an aerial life ; it had some resemblance to bats and birds, 

 but was widely different from both. In bats the whole anterior 

 extremity is elongated to form the framework of a wing, but in the 

 Pterodactyle it was only the little finger that was lengthened and 

 strengthened to become a rod for supporting a membrane, whilst the 

 other parts of the hand, the thumb aud three inner fingers, retain 

 their normal size. Like birds, the long bones of the arm are hollow 

 cylinders, and it differed from birds in having the skull of Eeptilia, and 

 its jaws were armed with long teeth implanted in distinct sockets. 

 The first Pterodactyle, Dimorphodon Macronyx, appeared in the Lower 

 Lias of Lyme Regis, and is another example of specialised osteology, 

 of which as far as is known no traces of ancestry can be found in the 

 Trias formation. 



The Teleosaurian, or land and river reptiles, appear in the Upper 

 Lias. Several examples of small specimens have been found in the 

 fish bed at Dumbleton, and in the same formation in Somersetshire, 

 as well as in the Upper Lias of Yorkshire. 



The wide contrast between the reptiles of the Lias and those of 

 the Trias was brought forcibly before me last summer when studying 

 the Wiirtemberg Ammonites in the Stuttgart Museum, where capital 

 specimens from both of these formations are introduced at the same 

 moment to the eye of the observer by being preserved in large 

 case3 placed on opposite sides of the saloon. After a careful study of 

 thes3 remains I failed to discover any genetic relations between the 

 fossil Eeptilia of these two periods of Mesozoic time. 



Fishes are very rare in the Lower Lias of this region, but the fish 

 bed of Dumbleton in the Upper Lias has yielded some fine large speci- 

 mens of Leptolepis, Pachycormus, and Tetragonolepis discus. 



The Cephalopoda form the highest class of the Mollusca, and are 

 remarkable for their abundance in the Lias, and for the important 

 part they played in the eventful life-history of that period. The class 



