THE FAUNA OP THE ST. JOHN GEOUP. 123 



typical Bohemian form so also does the Ctenocephalus, for in it the suture extends on the 

 underside only two-thirds toward the apex, but in Ct. cowmltis about seven-eighths. In 

 this genus also, as in Conocoryphe, the trilobites of the Acadian horizon present a peculiar 

 fades agreeing on both sides of the Atlantic, but differing from the species which appeared 

 in Bohemia, Spain and Britain in the Meuevian period. The wall-like front and crest of 

 Ct. coronatus are not foiiud in the Ctenocepaloid species of the antecedent period. The 

 fauna of Division Ic of the St. John group may, therefore, be said to contain within 

 itself evidence of a great antiquity, and at the same time is the richest in the number and 

 variety of forms of any assemblage of species of similar age. 



In conclusion, I would here return my thanks to seA'eral gentlemen who have aided me 

 in the investigation of these ancient fossils. To Dr. Henry Hicks I am greatly indebted for 

 copies of his papers on the Cambrian fauna of Wales and of others relating to the earlier 

 formations of G-reat Britain. To Mr. C. D. Walcott, of the United States G-eological Survey, 

 I am indebted for communicating in advance of publication the principal points of his 

 study of the type-specimens of the Cambrian species, described by Prof. Hartt, and now 

 deposited in Cornell University. I have to thank Prof Aljiheus Hyatt for information 

 respecting Ct. coronatus, and Mr. J. F. Whiteaves for affording me facilities at the Museum 

 in Ottawa. 



