TRENTON CONGLOMERATE OF RYSEDORPH HILL 113 



nomenon in this region, and even in Cambric beds close to the 

 Trenton conglomerate, can be entertained. Farther, the infer- 

 ences as to the origin of the intraforinational conglomerate 

 drawn bv Mr Walcott from observations extended over the 

 whole Appalachian region, seein to be applicable to the Ryse- 

 dorph hill conglomerate. Mr Walcott had the opportunity 

 of observing the relation of the bedded limestone to the super- 

 jacent conglomerate, a relation which proved that the calcareous 

 mud which was subsequently consolidated into the limestone, 

 solidified soon after deposition. " This is shown by the presence 

 in the conglomerate of rounded pebbles and angular fragments 

 of limestone with sharp clear-cut edges." The same observa- 

 tion has been made in the Rysedorph hill conglomerate as to the 

 lower Trenton pebbles.; and, as the same fauna has been found 

 by the writer in the matrix and in one of the groups of lime- 

 stone pebbles, the calcareous mud composing those pebbles must 

 have consolidated during the continued existence of that fauna. 



SUMMARY 



1 The investigation of the lower Siluric shales of the neighbor- 

 hood of Albany has led to the observation of a conglomerate bed 

 embedded in these shales and outcropping on Rysedorph hill near 

 Rensselaer, on the Moordener kill near Castleton and at Schodack 

 Landing. 



2 The most interesting feature of this conglomerate is the fauna 

 which the component pebbles and the matrix contain. To de- 

 scribe these and to obtain from them conclusive data as to the 

 age of the inclosing Normans kill .shales is the principal purpose 

 of this paper. 



3 The conglomerate contains a great variety of pebbles. In 

 the southern outcrops, at Schodack Landing, nonfossiliferous 

 sandstone pebbles prevail; going northward, fossiliferous lime- 

 stone pebbles increase, and on Rysedorph. hill thej^ are the prin- 

 cipal components. 



4 The limestone pebbles are shown by their faunas to be de- 

 rived, in very small number, from Cambric and Chazy rocks; 



