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NEW YORK STATE MUSEUM 



rhabdosomes of a considerable number of species 1 is a forcible 

 indication that they had fallen to the sea floor and drifted about 

 outside of their habitat. The assumption that the rhabdosomes 

 were carried by currents either oceanic, tidal or coastal, and 

 deposited, as suggested by Lapworth, in the quiet water at a 

 certain, more or less uniform, distance from the coast, can there- 

 fore not be far from the truth. We must conclude from their 

 meridional distribution that they were brought into the Appa- 

 lachian region from the Atlantic basin, while the far west 

 received them from the Pacific basin. 



Lower Trenton faunas of the central and eastern coastal regions with 



European elements 



The question of the probable route along which this incursion 

 took place, may at present be disregarded, and the mere fact 

 be emphasized that there exists a wide difference between the 

 fauna and sedimentation of part of the lower Trenton in the 

 eastern coastal region, and that of the eastern inland region. 

 This difference may be only one of faeies, that is, a difference 

 in faunal composition causally connected with the difference in 

 sedimentation, and may indicate nothing but difference of depth, 

 distance from the coast line or swiftness of current, such differ- 

 ences as are found within close limits along all coasts, and affect 

 only small areas. Or it may be one of provincial importance 

 caused by the differences of the conditions existing between 

 different parts of the ocean, or the latter and its border seas. • 



The wide extent of the Normans kill graptolite fauna and 

 its restriction to the eastern continental borders on one hand, 

 and the greater extension of the synchronous Trenton limestone 

 and its restriction to the continental platform, suggest that we 

 have here a difference of provincial importance. It is therefore a 

 fact of much interest that there is found entombed in the con- 

 glomerate a limestone fauna which must have existed shortly 



1 To illustrate this scarcity of colonies, it may be mentioned that in a dozen boxes of selected 

 material secured in a week's collecting at Mt Moreno near Hudson, not a single colony was found, 

 though all the species of the horizon are represented by rhabdosomes in finely preserved state. The 

 same experience has been repeatedly met with by the writer^ as well as others, in all localities of 

 this zone. 



