THE TRIASSIC PERIOD. 22 T 



just named, it is still doubtful whether they are genuine 

 reptiles, or perhaps Amphibia of the salamander kind. 

 Their skeleton alone is known to us, and even this not 

 perfectly. Now as we know nothing of the characteristic 

 features of their soft parts, it is quite possible that the 

 Proterosaurus and Rhopalodon were non-amnionate animals 

 more closely allied to Amphibia than to Reptiles ; possibly 

 they belonged to the transition form between the two 

 classes. But, on the other hand, as undoubted fossil remains 

 of Amniota have been found as early as the Trias, it is 

 probable that the main class of Amniota first developed in 

 the Trias, that is, in the beginning of the Mesolifchic epoch. 

 As we have already seen, this very period is evidently one 

 of the most important turning points in the organic history 

 of the earth. The palasolithie fern forests were then re- 

 placed by the pine forests of the Trias period ; important 

 transformations then took place in many of the classes of 

 Invertebrata. Articulated marine lilies (Colocrina) de- 

 veloped out of the plated ones (Phatnocrina.) The Autechi- 

 nidee, or sea-urchins with only twenty rows of plates, took 

 the place of the paheolithic Palechinidse, the sea-urchins 

 with more than twenty rows of plates. The Cystide^, Blas- 

 toidese, Trilobita, and other characteristic groups of Inverte- 

 brata of the primary period became extinct. It is no 

 wonder that transforming conditions of adaptation power- 

 fully influenced the Vertebrate tribes also in the beginning 

 of the Trias period, and caused the origin of Amniotic 

 animals. 



If, however, the two Lizard and Salamander-like 

 animals of the Permian system, the Proterosaurus and 

 Rhopalodon, are considered genuine Reptiles, and conse- 



