70 NEW YORK STATE MUSEUM 



not before noted in the specimen. The outer folds of the hydro* 

 spires were seen to extend under the interbrachials to the edges of 

 the bibrachials. The position of the stem was shown to be not 

 normal, as Billings supposed, but thrust up into the coelomic cavity 

 and separating the basals from the radials. There were no features 

 to show a specific difference between the Canadian type and the 

 more perfect Valcour island specimen, but the type served to corrob- 

 orate in a clear manner much of the detail worked out from the 

 latter and published in Bulletin 107 of the New York State Museum. 

 On Monday, July 8, the party went by train from Plattsburg to 

 Lyon Mountain, and spent the day studying the magnetite mines 

 under the guidance of Mr Newland. After lunch the section lis- 

 tened to a paper by D. H. Newland on 



The iron ores of the Adirondack region 



Four varieties of iron ores are found within the limits of the 

 Adirondack region, each constituting a more or less independent 

 class of deposits as regards geological associations and mode of 

 origin. The varieties are as follows : ( i ) nontitaniferous magnet- 

 ites, (2) titaniferous magnetities, (3) hematites, (4) limonites. In 

 respect to the relative age or period of formation, it is probable that 

 the magnetites of class i are the oldest, since they antedate the 

 metamorphism and structural disturbances that affected the region 

 during Precambric times. The titaniferous ores were formed before 

 the oldest of the fossiliferous rocks of the region (the Potsdam 

 sandstone) was deposited, and are generally regarded to be con- 

 temporaneous with the igneous inclusions in which they occur. The 

 hematite ores are probably later than the Potsdam; while the limo- 

 nites have the character of bog ores and are relatively recent sur- 

 face concentrations. 



The nontitaniferous magnetites are the most widespread of all 

 the ores in their geographical distribution, and have been in the 

 past and still are the main source of supply for the region. In a 

 strict sense they are hardly deserving of the name that has been 

 applied to them by geologists, since they nearly always carry titan- 

 ium, though the amount is small, usually but a fraction of one per 

 cent. These ores are found in all parts of the Adirondacks, except 

 the central which is occupied by the great gabbro-anorthosite mass. 

 They are associated with different members of the Precambric crys- 

 talline series including gneisses of igneous derivation with the 

 mineralogy of granites and syenites, with gneisses of doubtful re- 



