424 



troxell: fossil birds eggs 



surfaces of the calcite crystals. On the other hand the space 

 within the calcite may have been left when the growth of the 

 crystals had reached its limit, or it may have been occupied by 

 the desiccated resi- 

 due of the egg ma- 

 terial. The inner 

 surface of the geode 

 is lined with minute 

 crystals of quartz. 



SECOND SPECIMEN 



The second speci- 

 men of fossil egg was 

 flattened to about 

 three fourths its 

 former diameter; be- 

 cause of this distor- 

 tion and because of 

 the total absence of 

 silica it presents some 

 added points of interest. The dimensions are: Length 61 mm., 

 width 48 mm., thickness 34 mm. 



The hump, as shown in figure 4, appears to be a result of 



rigid opposition in the 

 center while the edges 

 were forced down. In 

 reality it is simply the 

 normal arch displaced. 

 There was pliable re- 

 sistance within the egg ; 

 the strain, therefore, 

 which shortened the 

 vertical diameter re- 

 sulted in an increase 

 in the horizontal di- 

 mensions ; quite probably the volume did not change appreciably. 

 Except for this there would have been real crushing or caving in 

 without a corresponding increase in size laterally. 



Fig. 3. Fossil egg ; second specimen. Top view, 

 about natural size. The very rough surface is un- 

 like that of most modern eggs. The cracks in the 

 edge as well as the change in form indicate the ex- 

 tensive crushing. 



Fig. 4. Side view of specimen shown in figure 

 About natural size. 



