After this statement von Meyer gives a discursive summary, in which his views of the classification of reptiles in general and of Pterodactyles in particular are epitomized. And then goes on to combat the views of people who have departed from his classification and attempted to set up classifications of their own; and cites a number of authors who, labouring at the vertebrata, have endeavoured to find a resting-place in their systems for the Pterodactyle. But the chief thing we learn of von Meyer's own views is, that in 1830 he published a classification of extinct Saurians, dividing them into those with limbs like the larger and heavier land-mammals, those with fin-like limbs, and those with a flying-finger. Which divisions have been widely adopted, though authors have sometimes given them other names than those by which they were first made known. Von Meyer has freely stated the facts about the Pterodactyle, and draws the conclusion that the animal was a reptile; but how such a conclusion was obtained from such facts is a matter on which his pages are silent. One seems to hear the chirrup of the bird in almost every paragraph. The head is in the main a bird's head; the pectoral girdle and the sternal ribs are those of a bird; and very few are the structures in which some reminder of the bird is not present; and in their bones he discovered the pneumatic characteristic and inferred, for the animals bird-like lungs. How, then, comes it that the Pterodactyle is a reptile? We can only suppose the answer to be, Because if the head and pectoral girdle and other bones had been reptilian it would have been a bird. * * * * * In the views here epitomized it is difficult always to make out the logical foundations of the conclusions arrived at. Sometimes they have no foundations, and sometimes they represent the different aspects in which a truth presents itself to minds differently constituted or differently conversant with the structures of living animals. In now stating my own views I shall avail myself of the example of some previous writers, and attempt to investigate the Pterodactyle as though they had not written. And then, having placed before him all the theories that are known, the reader will be able to choose the theory that pleases him best, if indeed he needs one.