268 Canadian Record of Science. 



regions it seems to be absent. Its geographical distribution is 

 in fact to a great extent parallel with that of the middle and 

 upper Paradoxides zone ; and if these latter owe their pre- 

 sence to cold arctic waters, we may attribute to the same 

 cause the distribution of the Peltura fauna along the coast 

 of America in Cambrian times. The Cambrian fauna of the 

 Liau-tung has not a sufficiently wide range to make it cer- 

 tain that Peltura sub-fauna may not overlay it. But if the 

 succession of Cambrian trilobites, as established in 

 Europe, is to be relied upon for other countries, this fauna 

 is absent from Minnesota, and probably from the Eocky 

 Mountain region of the United States. Neither in Bohemia, 

 nor at any point in the south of Europe has this phase of 

 the Upper Cambrian fauna been met with. 



In the absence of the Peltura fauna the lines dividing the 

 different parts of the Upper Cambrian are but obscurely de- 

 fined, and for the southern countries we have not yet dis- 

 cerned the land marks by which this division may be 

 effected. Only in the western United States is there known 

 a full representation of the southern types of the Upper 

 Cambrian faunas, and here we may hope that these dividing 

 lines will soon be drawn. Prof. Jas. Hall many years ago, 

 described the Cambrian trilobites of the Mississippi Valley. 

 He divided them into three faunal groups of which the upper 

 by its fades, appears to be equivalent to the Tremadoc fauna. 

 Yarious considerations render it probable that the middle 

 fauna, which Prof. Hall intimates might hereafter be sub- 

 divided, includes all the lower part of the Upper Cambrian, 

 so that the Peltura fauna would be excluded. In the middle 

 fauna of the Mississippi Valley a peculiar type of Agnostus 

 which in Sweden is represented by A. cyclopyge of the 

 Oienus beds, is here present in A. Josepha, and in China by 

 A. Chinensis. These Agnosti are associated with species of 

 other genera which are particularly prevalent at the hori- 

 zons of the Oienus and Dolgelly beds, and thus carry the 

 series of forms down to the Lower Cambrian division with- 

 out the presence of Peltura. 



As a result of the comparisons attempted in this paper it 



