100 GEOLOGY OF THE SECOND DISTRICT. 



the New-York Survey, are the lowest beds of the Transition System ; they rest immediately 

 upon the Primary, and though among themselves there is no unconformability, yet in many 

 minor districts they are quite disturbed and broken up, especially near the line of junction 

 between the transition and primary rocks. As we recede from this line to the deeper parts 

 of the transition, they become quite regular, being scarcely disturbed or moved from the 

 original position in which they were deposited. 



As the rocks which constitute the lower part of the mass of the Transition system have 

 hitherto received very little attention, it became necessary not only to investigate with great 

 care their characters and relation, but also to provide them with suitable names. After having 

 given them the attention and care they seemed to require, I have, with little hesitation, con- 

 cluded that they belong to but one group. Although there is a great diversity in the litholo- 

 gical characters, still the fossils appear to belong to but few types, and to those which are 

 strictly related to each other. In this single group, the fossils appear to be allied ; but when 

 we leave the upper member, and pass to the Medina sandstone, we find a distinct change in 

 the character of the fossils. It is here we first meet with the Fucoides harlani ; but up to 

 this rock, certain genera and species of shells run through the entire mass, as Leptaena, Or- 

 this, Atrypa, Delthyris, &c. Although these genera are not confined to the lower rocks, yet 

 certain species, with very few exceptions, are confined to this lowest group ; and it is not only 

 so wilh the Testacea, but also with the Crustacea ; thus, the species belonging to the genera 

 Isotelus, Trinuclcus, Calymene, lUenus, etc. are mostly confined to it. One remarkable 

 Polyparia, known as the Fucoides demissus, appears to belong, so far as researches have yet 

 extended, to these lower rocks. I do not, however, propose in this place to go into the cha- 

 racters of this group : the individual members will be described in their proper places, when 

 I shall give a full account of their fossils, and the characteristic features of the several rocks 

 composing them. 



The name which appeared the most appropriate to this group, is derived from the lake along 

 which they are so well developed, (I refer to Lake Champlain) ; hence it becomes the Cham- 

 plain group. Although it would have been perhaps desirable to have selected one from a 

 town or locality, still there appear to be no strong objections to its use and adoption. In the 

 first place, all the rocks and masses, without exception, are found not far from its borders ; 

 and besides this, the whole is so accessible, that it is no small recommendation to its adoption. 

 The name, too, is one which may well be considered less local than anj' other which could be 

 selected : it is, as it were, a national name. Surrounded as it is by allied rocks, and bordered 

 by two States, and extending into one of the British Provinces, it appeared more likely to be 

 sanctioned than one derived from any locality within the limits of the Second District. 



Following out the plan of the nomenclature for the rocks of New-York, I have considered 

 that, for purposes of study, they might be arranged in four groups, as follows : Champlain 

 group, at the base of the Transition system ; Ontario group, comprehending the rocks which 

 lie upon its southern border for about fifteen or twenty miles ; the Helderbergh series ; and 

 lastly, the Erie group, which completes the whole series of the system, extending up to the 

 old red sandstone. These four groups are tolerably well defined : they are, at least, so loca- 



