Fossils of ancient As]jed. 59 



marble occurring on some of the moraines have had sucli a source. 

 Tavo large calcite seams of this character show beautifully on the 

 eastern face of Pyramid peak, looking, to an observer in Dying 

 glacier valley, like rills of water on the mountain side. In the 

 vicinity of the eruptives these fissures are often metalliferous, 

 and occasional quartz veins occur. 



Careful search for fossils was made in these argillites at many 

 points, but no discovery rewarded the search. It is very possi- 

 ble that the series comprises rocks of more than one age. The 

 whole is so homogeneous in appearance that its dissection, if 

 dissection is possible, will ha a matter of vast and painstaking 

 labor. 



The Limestone. — The mountains forming both shores of the larger 

 part of Glacier bay, and all the islands in the bay except the two in 

 Muir inlet and the Beardslee islands, are made up of metamorphic 

 limestone. This first appears on the eastern side of the bay, form- 

 ing the mountain peak just south of the peak of mount A\^right, 

 follows along the mountain summits for some little distance with 

 slight dip. and then abruptly plunges down to the shore with a 

 very steep southerly dip. Near its contact with the slates it con- 

 tains considerable argillaceous admixture ; otherwise it is an ex- 

 tremely pure dolomitic limestone, containing only a trace of 

 insoluble matter. More commonly it is of a dark purplish tint, 

 though some portions are drab. It is cut by the same fissure 

 systems as the argillites, but is bound into a more compact mass 

 by the calcite which everywhere completely fills the fissures, so 

 that it disintegrates with le-^s rapidity. Search for fossils in the 

 limestone was rewarded at only one locality, on the island in 

 Glacier bay nearly due south of Headland island. Here but a 

 handful were found. The only recognizable forms were shells of 

 Leperditia. Sections of large gasteropods showed beautifully on 

 the highly polished limestone surface, but it was impossible to 

 break out specimens which would give any indication of external 

 form. I sent the collection to Professor H. S. Williams for ex- 

 amination. He replied that LepercUtia was recognizable, while 

 the others would scarcely repay careful examination ; that the 

 age was probably Paleozoic, but that the collection would war- 

 rant no more decisive statement. The superior limit of the lime- 

 stone was not seen, but it has a thickness of several thousand 

 feet. It appears conformal)le with the argillHes below, indicating 

 their probable Paleozoic age. 



!l— Nat. CiEOfi. Mac , voi,. IV, ISIIl'. 



If 



