98 GEOLOGY. 



9 



traordinary that they soon outranked the carnivorous forms both in 

 size and diversity. The sauropoda were generally massive animals, 

 with sub-equal limbs and the quadruped habit. Among these, Bronto- 

 saurus (Apatosaurus) attained the extraordinary length of 60 feet 



Fig. 371. — A carnivorous dinosaur, Ceratosaurus nasicornis, about T V riatu'al size, 

 i.e. length about 17 feet; from the Como beds, Colorado. (Restoration of skele- 

 ton by Marsh.) 



and possibly more, taking rank as one of the largest of known land 

 animals (Fig. 372). This enormous creature was characterized, never- 

 theless, by weakness rather than strength. The general organization 

 was unwieldy; the head was very small relatively, the brain having 

 less diameter than the spinal cord. " The task of providing food for 

 so large a body must have been a severe tax on so small a head." The 

 inconvenience of its bulkiness was perhaps relieved by an aquatic 

 habit. From the fact that its skeleton is sometimes found in a nearly 

 complete and orderly state, it has been inferred that the creature was not 

 infrequently the victim of 'its own massiveness, and lost its life by 

 sinking in some soft, treacherous shoal. This colossal animal may be 

 taken as illustrating the point at which bulk becomes a burden, and 

 as signalizing an approach to the limit of evolution in the line of size. 

 Even larger than Brontosaurus, and the largest of all known dinosaurs, 

 was Brachiomurus, of which the femur measured more than two meters 



