1 882.] Evolution of Forms from Clinton to Niagara Group. 711 



larger than in autumn, the weight is nearly twice as great. Their 

 physiological activity culminates with the maturing of the ova 

 and the labor of depositing it ; this effected, they are worn out 

 and in a very short time, die. 



THE EVOLUTION OF FORMS FROM THE CLINTON 

 TO THE NIAGARA GROUP. 



WHILE collecting Niagara and Clinton fossils in the village of 

 » » Gasport during the fall of 1 881, I was struck by the pecu- 

 liarity of texture and character of the fossils contained in the 

 upper band of limestone ; which is there found superimposed 

 upon the series forming the upper portion of the Clinton group 

 proper, and I at once recognized a similarity between its fauna and 

 structure, to an analogous layer which I had previously noticed 

 in the western portion of the town of Lockport, but had failed to 

 find at several other points of outcrop. 



At the place where it was first noticed, however, its character, 

 both in regard to the fossils contained, which there are generally 

 rare and fragmentary, and the general appearance of the rock, 

 is not so pronounced in distinction from the underlying strata 



This layer is not continuous, but apparently occurs in confined 

 areas. Thus it is found at Gasport and again in the western por- 

 tion of the town of Lockport. But in the city, about two miles 

 east from the latter point, and on the same line of outcrop, whose 

 general direction is from east to west, it is entirely wanting, as I 

 have ascertained by a careful examination of both natural and 

 artificial exposures at the line of juncture between the Niagara 

 shale and Clinton limestone. 



It is extremely variable in thickness, but I should judge its 

 greatest development to be in the neighborhood of two feet. 

 This is merely to be taken as an estimate, as I have not been 

 able thus far to take the proper means of obtaining accurate 

 measurements. 



The upper surface is extremely irregular and undulating ; hav- 

 ing the appearance of being drifted together. This is also cor- 

 roborated by the position of many of the fossils, which seem to 

 have been swept together by eddies, which at the same time were 



