220 THE POPULAR SCIENCE MONTHLY. 



the creature specifically light in its flight. Like a bird, this creature 

 has a largish breastbone, but from that point onward, so far as I can 

 see, special, particular resemblances end, and a careful examination 

 of the fore-limbs shows you that they are not birds' wings ; they are 

 something totally different from a bird's wings. And then, again 

 (pointing to a chart), those are not a bird's posterior extremities, but 

 are rather a reptilian's hind-limbs. The vertebras present nothing 

 that I need dwell upon, but the bones of the hand are very won- 

 derful. 



There are four fingers represented. These four fingers are large, 

 and three of them these, which answer to these three in my hands 

 are terminated by claws, while the fourth is enormously prolonged 

 into a great jointed style. You see at once from what I have stated 

 about a bird's wing that there could be nothing more unlike a bird's 

 wing than this is. It was concluded by general reasoning that this 

 finger was made to support a great web like a bat's wing. Speci- 

 mens now exist showing that this was really the case, that this creat- 

 ure was devoid of feathers, but the fingers supported a vast web like 

 a bat's wing, and there can be no doubt that this ancient reptile flew 

 after the fashion of a bat. Thus, though the pterodactyl is a flying 

 reptile, although it presents some points of similarity to birds, yet is 

 it so different from them that I do not think that we have any right to 

 regard it as one of the forms intermediate between the reptile and the 

 bird. Such intermediate forms are to be found, however, by looking 

 in a different direction. Through the whole series of mesozoic rocks 

 there occur reptiles, some of which are of gigantic dimensions ; in 

 fact, they are reckoned among the largest of terrestrial animals. 

 Some of them are forty and fifty, possibly more, feet long. Such are 

 the Iguanodon, the Megalosaurus, and a number of others, with the 

 names of which I will not trouble you. There are great diversities 

 of structure among these great reptiles. Some of them resemble liz- 

 ards in the proportions of their limbs, and have evidently walked on 

 all-fours, in that respect resembling the existing crocodile ; but in 

 others you can trace a series of modifications in virtue of which the 

 hind-limbs at length completely assumed the character of a bird's 

 hind-limbs. I here indicate (pointing to a diagram) the hind limb 

 of a crocodile, showing the bones of the hind-limbs and of the pelvis. 

 These are the haunch-bones ; these are the two leg-bones. Then 

 comes the division of the foot which we call the tarsus, in which the 

 component bones are separate and distinct from one another, from 

 the bones of the les: and from those of the metatarsus. Then come 

 the four toes, which alone exist in the hind-feet of the crocodile, and 

 which are separate and distinct. The foot is flat on the ground, so 

 that the legs spread out and the weight of the body hangs clumsily 

 between them. Contrast this with what we find in the bird the 

 haunch -bone here is immensely elongated, and the joints of the 



