190 MAMMALIAN DESCENT. [Lect. VIIL 



and to draw out tlie Flying Cat's skin into a parachute, 

 without imagining further and further degrees of the 

 same processes, which, being continued, would inevitably 

 end in the formation of a Bat. If the palaeontologist had 

 not demonstrated these things to us, we should never 

 have conceived of the Pterodactyles, or winged Reptiles, 

 that swarmed in the Secondary epoch ; the contem- 

 poraries, let me remind you, of the Marsupials of our 

 own region. Then, towards the end of that period, the 

 northern hemisphere abounded in Birds quite unlike our 

 horny-beaked, toothless types. These had jaws weU 

 furnished with teeth, some of them had teeth standing 

 against the jaw wall (Pleurodont), whilst others had 

 socketed teeth (Thecodont) ; both these methods of tooth- 

 fixture stUl remain in existing' Eeptiles. Further back a 

 little, in the times of the Upper Oolite, Birds existed with 

 a long tail like that of a Lizard, and with the bones 

 of the hand distinct, as in the Lizard, and not melted 

 together, as in the wing of the modern Birds. The flying- 

 Lizard (Pterodactyle) shot out one finger into a long, 

 jointed rod, and to this rod the skin forming the wing 

 was attached, like a sail. We are all familiar with the 

 Bat, and a summer evening's walk would lack one of its 

 charms if no Pipistrelle flitted past our face on his moth- 

 hunting raids. But what an excitement there would 

 have been amongst the astonished palaeontologists if 

 the Bats had been all extinct, and just one should have 

 rewarded the labours of a Marsh or a Cope ! The Bats 



