272 ANNALS NEW YORK ACADEMY OF SCIENCES 



A new locality for pyrite was found in the past few months at the Ibex 

 Mines, Colorado. The crystals are of special interest because of their 

 magnificent character and their frequently hemamorphic shape, two of the 

 four faces being entirely cubic (a) and the plan of the crystals pentagonal 

 dodecahedrons (e). The crystals are unusually compact of type cut into 

 small jewelry and sold under the name of "marcusite" in the early part 

 of the eighteenth century. One of the crystals weighed more than two 

 pounds. 



An irregular, cubic crystal of black diamond, weighing 138.75 carats 

 and measuring 23.5 millimeters on each face, 11 millimeters in width and 

 6 millimeters in depth was found at the Jagersfontein mine. Although 

 of cubic form, it is built up of rounded octahedral conglomerations. 



Professor Finlay stated that North Park is located near the boundary 

 line of Colorado and Wyoming. The rocks are of sedimentary and vol- 

 canic origin. The platform upon which the sediments rest is largely 

 made of granite, and there are considerable amounts of gneiss and schist, 

 and then comes the Parrell limestone, which is about 30 feet thick. 

 Above it one finds about 1,500 feet of red sandstone. Next comes the 

 Morrison, about 260 feet in thickness, and above this the Glen Cairen 

 shales. Then comes the true Dakota, about 100 feet thick, and above is 

 a rather complete series of Cretaceous beds, closing with the Pierre shales, 

 2,500 feet thick. The chief economic deposit found here is coal, which 

 is quite phenomenal, having a thickness of 50 feet in some places in the 

 Coalmont formation. Very little of it is mined, however, since it is too 

 soft for commercial purposes. 



The paper was discussed by Dr. Johnson and Mr. Knight. 



Professor Grabau stated that the structure of the island of Gotland is 

 very simple, being composed of slightly tilted limestone and shale beds 

 with no faults in evidence. It is very rich in fossils. The Cambric, 

 Ordovicic, and Siluric beds were deposited in this region in normal 

 sequence. Subsequently the region was submerged beneath the water of 

 the Baltic, except for the island of Gotland. Here two series of forma- 

 tions are in evidence, a lower in the north and an upper in the south. 

 These two series, however, do not correlate one with the other, as some 

 European geologists have tried to prove. Professor Grabau believes that 

 the higher series in the south correlate with the Lower Ludlow of the 

 English section. There is a break between the Upper and Lower Ludlow 

 in Europe which is represented in America by the Salina. The Upper 

 Ludlow is the equivalent of the Monroe of Michigan. The Lower Lud- 

 low, Wenlock and Llandovery correspond to the American Niagara and 



