' HUDSON RIVER BEDS NEAR ALBANY 551 



1 Lorraine beds 



2 Utica beds 



3 Upper and middle Trenton beds 



4 Dicellograptus beds; these resting on 



5 Lower Trenton limestone 



The legitimate conclusion to be drawn from this succession of 

 l^eds is that the Dicellograptus zone is liomotaxial icith a part of 

 the middle or loioer Trenton limestone. This conclusion stands in 

 iull accord with the evidence furnished by the conglomerate beds. 



None of these zones, however, is entirely uniform in its fossil 

 contents, as a comparison of the fossils from the various stations 

 easily demonstrates. Not taking into account the difference be- 

 tween graptolite and mollusk beds which may be synchronous, 

 run into each other and alternate irregularly, it is evident that 

 the associations of fossils in some beds differ greatly from the 

 typical faunas of their epoch. 



There is first the difference between the typical lower Dicello- 

 graptus beds and the Dicellograptus beds of Mt Olympus and 

 Lansingburg; farther the remarkable admixture of Trenton fos- 

 sils and the presence of the Olimacograptus caudatus, 

 which is a typical upper Dicellograptus form, in the Utica beds 

 of Mechanicsville, and the appearance of Cryptograptus 

 tricornis among the Utica fossils of Van Schaick island. 

 These latter faunas differ markedly from the typical Utica grap- 

 tolite fauna of the Rural cemetery, the penitentiary and the lower 

 Normans kill. There is finally the peculiar combination of Tren- 

 ton and Lorraine forms with the Utica fauna of the old observa- 

 tory and Green Island. 



The full list of the various faunas observed is the following: 



Lower Trenton fauna of conglomerate beds of Rysedorph hill, 

 consisting at least of three different faunules 



Typical lower Dicellograptus fauna 

 rp Lower Dicell. fauna of MtOlym- [Relative position of 



pus and Lansingburg -j these two faunas not 



[ Dipl. anaplexicaulis fauna [ yet clearly determined 



