110 LECTURES ON BIOLOGY 



gigantic forms of extinct Saurians never fail to impress us. But 

 whilst reptiles reached the zenith of their development during 

 the Mesozoic and particularly the Jurassic Period, mammals are 

 flourishing and developing gigantic forms in our time. 



In spite of its terrifying appearance the Brontosaurus must 

 have been very harmless. It was herbivorous. Remarkable is 

 the head, the smallness of which is ludicrously disproportionate 

 to the mighty body. It was probably a slow, awkward animal, 

 of a low mental development. We may also mention among the 

 land animals the Stegosaurus, distinguished by a dorsal series of 

 large erect bone-plates, the gigantic Iguanodon, and individuals 

 of the Ceratopsidse whose skull was crowned with horns of an 

 enormous size. 



Not only land and water but also the air has been subjugated 

 by the Saurians of the Mesozoic Period. Most famous among the 

 Pterosaurians are the Pterodactyls. Their size varies between 

 that of a sparrow and an eagle. Their bones are hollow, like 

 those of birds, the structure being generally adapted to a life in 

 the air. As in the bat, the flying organ is formed by the anterior 

 extremities, the outer of the four digits being enormously elon- 

 gated. Its object was to extend the flying membrane proceeding 

 from the trunk and posterior extremities (see Lecture I.). A 

 gigantic flying-saurian, the Pteranodon, has been found in North 

 America. It measured 8 metres from tip to tip of the extended 

 wings. 



In the Jurassic Period we encounter for the first time a bird- 

 like organism, the Archseopteryx. It was discovered nearly fifty 

 years ago by workmen in the lithographic stones near Solenhofen, 

 the scene of many other important finds. Though only a few 

 fragments had been preserved of this strange feathered animal, 

 it was purchased by the British Museum in London for the large 

 sum of 600. Owing to the incompleteness of the skeleton, 

 opinions were long divided concerning the nature of this unique 

 being ; some declared it to be a bird, others a reptile. Several 

 years afterwards another much better preserved specimen was 

 found not far from the scene of the first discovery and deposited 

 in the Berlin Museum of Natural History (fig. 27), forming one 

 of its most valuable possessions. With this discovery the position 

 of the Archseopteryx in the system was definitely recognized. 



