PROGRESSIVE PERFECTION. 177 



Lestornis). Possibly in future days we shall be able by the dis- 

 covery of new types to establish the connection with the Dino- 

 murians (Compsognathus), the formation of whose pelvis and feet 

 offers a closer relationship to those parts in birds. 



Advance towards perfection. If we compare the animal and 

 vegetable life of the most ancient formations with that of the sue 

 ceeding periods of the earth's development, it becomes evident that 

 there has been, on the whole, a continual progress from a lower to a 

 higher condition. The oldest formations of the so-called archsean 

 time, the rocks of which are for the most part in a metamorphic 

 state, must from their enormous thickness have occupied immea- 

 surable time in their origin. They contain no fossil remains which 

 can be recognised with certainty as such ; although the presence of 

 bituminous gneiss in the old formations is a proof of the existence 

 of organic bodies at that time. All the organisms of these most 

 ancient periods, which were certainly numerous, have been de- 

 stroyed without leaving any further traces than the Graphite 

 deposits of the crystalline schist. In the most ancient and very 

 extensive groups of strata we find exclusively cryptogamous plants, 

 especially Fuci, which formed extensive forests beneath the sea. 



The warm seas of the primary period were inhabited by numerous 

 sea animals of very different groups, such as Zoophytes, Molluscs 

 (especially Brachiopoda\ Crustaceans (larva-like Hymenocaris, Trilo- 

 bites), and Fishes whose peculiar armoured forms (Cephalaspidce) 

 indicate a low stage of organization. In the coal formations we 

 meet for the first time with the remains of land animals, Amphibia 

 (Apatheon, Archegosaurus), with a notochord and a cartilaginous 

 skeleton ; we also find Insects and Spiders; and in the Permian 

 formations we meet with large lizard-like reptilian forms (Protero- 

 saurus); while fishes, exclusively Elasmobranchs and Ganoids with 

 a notochord, and vascular cryptogamous plants (Tree-ferns, Lepido- 

 dendra, Calamites, Sigillaria, Stigmaria) still predominate. 



In the carboniferous period isolated instances of the Lizards 

 amongst Vertebrates and of Coniferse and Cycadiae amongst plants 

 had already made their appearance ; but in the secondary period they 

 obtained such a preponderance that the whole period has been named 

 from them the period of Saurians and Gymnosperms. Amongst 

 the first the colossal Dinosaurians living upon the land, the flying 

 Lizards or Pterodactyls, the Halosaurians, with their best known 

 genera Ichthyosaurus and Plesiosaurus, are entirely peculiar to the 

 secondary period. 



12 



