136 Discoveries in the St. John Group. 



II. Recent Discoveries in the St. John GKOUP.f 



By G. F. Matthew. 



For some years the St. John group has been known as a for- 

 mation containing the fullest representation of the oldest Cam- 

 brian fauna yet discovered in America. 



In Europe this very old fauna is well known, but in America 

 the Cambrian rocks which are best known and have been most 

 carefully studied, do not contain it. These Cambrian rocks of 

 America are known as the Potsdam sandstone ; they cover exten- 

 sive areas along the valley of the St. Lawrence and in the Middle 

 and Western States, and are thus the oldest Cambrian group recog- 

 nized by its fauna in the central region of North America, but 

 they do not contain any of the species of the St. John group. 



On the shores of Lake Champlain and along Hudson River 

 another group of Cambrian rocks is found, older than the Potsdam 

 sandstone, but even this, so far as we know, contains none of the 

 St. John species. In short, nowhere west of the Appalachian 

 Mountains have Cambrian strata been met with containing 

 remains of animals of the ancient type of those of the Acadian 

 provinces. 



The crustacean genus Paradoxides is one of the most character- 

 istic forms of this early fauna, and it has thus far been found in 

 America only to the east of the Appalachian chain. One 

 species is known to occur in Massachusetts, and three in Newfound- 

 land, but the genus is represented by a greater variety of forms at 

 St. John, N. B., than elsewhere on this continent. This genus is 

 considered to be characteristic of the Lower Cambrian rocks. 

 The late Professor C. F. Hartt, by a study of the fossils of the 

 St. John group, was able to declare that they were of the same 

 type as those of the Primordial zone in Bohemia, which Joachim 

 Barrande had shown to contain the oldest of all known organic 

 remains.* But, since Prof. JBartt made this determination, the 

 fauna of the Primordial zone has been further elaborated, and 

 Paradoxides is now found to mark the lower part of the Primor- 

 dial or Cambrian system. This fact was ascertained for central 



t From the Bulletin of the Natural History Society of St John, New 

 Brunswick, read December 2, 1884. 



* That is, the oldest known at that time. 





