TRIASSIC PERIOD. 



533 



numerous footprints, which have generally been referred to 

 Birds (Brontozoum), along with the tracks of undoubted Rep- 

 tiles (Otozoum, Anisopus, &c.) 



LIFE OF THE TRIASSIC PERIOD. The Triassic period, as 

 regards its plants and animals, is in many respects intermedi- 

 ate between the Palaeozoic and the later Mesozoic deposits, 

 whilst being itself decidedly Mesozoic. Amongst the plants 

 there are some Palaeozoic types (such as Calamites) ; but there 

 is no longer a marked predominance of Cryptogams, and the 

 leading forms are Ferns (Pecopteris, Neuropteris, Acrostichites , 

 &c.), Cycads (Pterophyllum, Podozamites, &c.), and Conifers 

 (chiefly belonging to the genus Voltzia). 



The Protozoa are represented in Triassic times by several 

 sponges (AmorphospongiO) Cupulispongia, Leiospongia, &c.) 

 Corals are by no means infrequent in the Muschelkalk, and in 

 some of the limestones of the Upper Trias ; but they are other- 

 wise rare. They belong mostly to Secondary types, such as 

 Montlivaltia, Synastraa, Acrosmilia, Eunomia, &c. The Echi- 

 noderms are rarely abundant, but two forms are exceedingly 

 characteristic of the Muschelkalk. These are the beautiful 

 Lily-encrinite, Encrinus liliiformis (fig. 80), and the little 

 Ophiurid, Aspidura loricata (fig. 71). 



Articulates are not abundant, with the exception of Ostra- 

 coda, which are sometimes very plentiful. The other common 

 forms are referable to Estheria; but Macrurous Decapods have 

 also been detected. Besides Crustaceans, several forms of 

 Insects have been discovered. 



The Mollusca are exceedingly abundant in parts of the Tri- 

 assic series, and they exhibit an extraordinary intermixture of 

 Palaeozoic and Mesozoic types. This is shown in a synoptical 

 manner in the following table of the Mollusca of the Upper 

 Trias of the Austrian Alps, given by Sir Charles Lyell in his 

 ' Elements of Geology : ' 



Genera of Fossil Mollusca in the St Cassian and Hallstadt Beds. 



Common to Older Rocks. 



Cyrtoceras. 



Orthoceras. 



Goniatites. 



Loxonema. 



Holopella. 



Murchisonia. 



Euomphalus. 



Porcel lia. 



Megalodon. 



Cyrtia. 



