54 MATTHEW. 



But the Etcheminian is not such a fauna as that described 

 by Dana, for it has the marks of advancement and develop- 

 ment in it and the dominance of one class over others. The 

 Hyolithidae had at this time reached as high a development 

 structurally as they ever attained. While not having the 

 diversity of ornamentation, or varieties of shape which they 

 afterward exhibited, they had already reached a high standard 

 as regards their general structure. Gerard Holm, in his stand- 

 ard memoir on the Hyolithidae and Conulariidae of Sweden, 

 divides Hyolithes (sens, strict.) into two great sections, viz : 

 Eqiddorsati, in which the boundary between the real dorsal and 

 ventral sides is at the lateral edge of the shell ; and Magnidor- 

 sati in which the real division between these two sides (/. e., the 

 place where the growth-lines change their course) is on the- 

 dorsal. Both of these sections are found among the Hyolithes 

 of the Etcheminian Fauna. The Hyolithidae then were highly 

 developed in this fauna, and dominated all other forms, burrow- 

 ing worms excepted, in numbers and size. 



5. Extension of the Etcheminian to the Westward. 



Having found the physical history of the Etcheminian terrane 

 so constant and parallel in the two regions of New Brunswick 

 and Newfoundland, 600 miles apart, I took advantage of an op- 

 portunity presented to me through the courtesy of Prof. W. O, 

 Crosby, at the time of the meeting of the American Association 

 for the Advancement of Science in Boston, to see the shales at 

 Braintree. Dr. Crosby first showed me the red slates near 

 Braintree which have been referred to the Olenellus zone, and I 

 was at once struck by their resemblance to the Etcheminian of 

 Newfoundland. These slates are said to underlie the trilobite 

 slates of Braintree, but they are separated from these by a granitic 

 intrusion ; this granite has so far affected the calcareous masses 

 found in the red slates that the borders of such bodies are epi- 

 dotized and the rock has an appearance of greater antiquity than 

 the red shales and slates of Newfoundland. But there are the 

 same occasional limestone beds and the same la}'ers beset with 



