540 



Karl A. Grönwall. 



nature and formation of this rock. Fig. 6, shows a microphotograph 

 of this rock, the section taken a right angles to the stratification. 

 It shows clearly that the rock consists of rolled fragments of various 

 parts of fossils, inbedded in a matrix consisting chiefly of crj^stal- 

 line calcite. These "pebbles", however, do not consist entirely of 

 rolled fossils and fragments of fossils, but also of parts of a rock 

 containing fossils; i.e., the products of the degradation of a rock 

 that was already solidified. Among the fossils that can be deter- 

 mined with certainty, Fusulinœ and other foraminifera are speci- 

 ally numerous, be- 

 sides which there 

 also occur frag- 

 ments of bryozoa 

 and crinoids. Of 

 inorganic matter 

 there are numer- 

 ous small grains 

 of quartz, about 

 0.1 mm. in size. In 

 some laminæ the 

 quartz is more 

 prominent, so as 

 to form almost 

 a sandstone, as 

 shown in the up- 

 per part of fig. 6. 

 The white lime- 

 stone (iV.o /:/ 2) has, 

 megascopically, 



Fig. 7. Slide of the white crystalline limestone, specimen very little resem- 

 N:o 112, from the Cape Jungersen section. Enlarged 15 diam. blance tO the ГОСк 



just described, it 

 being an entirely white rock of almost crystalline appearance, with 

 small cavities spread within the mass; the fracture of the rock is 

 uneven but, even with the aid of a pocket-lens magnifying to ten 

 diam., it is impossible to distinguish with certainty the constituent 

 parts of the rock. Under the microscope, on the other hand, the 

 real nature of the rock becomes very clear, and the microphotograph, 

 Fig. 7, gives a good representation of its appearance. It is seen at 

 once that the original formation of this rock is almost analogous 

 with that of the rock described above, but that it has undergone a 

 more complete diagenesis than the latter. The "pebbles" found here 

 are somewhat larger, and sometimes even exceed 3 mm. in length; 



