M ORO AN-T A LLM ON . 1 



A Fossil Egg from Art zona. 



405 



fills the pits completely. The number of pits in any piece of the 

 matrix corresponds in general with the number of visible pores 

 in that part of the shell from which it was removed. (PI. 48, 

 fig. 1.) These pores in the shell are also tilled with tar, and 

 the relative distribution of pits and pores over corresponding 

 surfaces of matrix and shell is the same. Opposite a fine crack 

 in the shell the quantity of tarry material is considerably 

 increased. Chemical examination failed to show the presence of 

 any tar in the matrix except this small quantity on or near the 

 surface in contact with the shell. 



THE EGG SHELL. 



The egg shell has retained its original composition and micro- 

 scopic structure. A chemical analysis shows that it does not 

 differ from the shell of a wild goose egg. A thin section (PI. 49, 

 fig. 2a) shows the same structure as that exhibited by a similar 

 section from a hen's egg. 



The form of the egg has been perfectly preserved, and from 

 comparison with existing eggs we conclude that this specimen 

 belonged to an aquatic bird. The egg corresponds fairly well to 

 the type of egg laid by the cormorant. Objection might be 

 made that the cormorant's egg is covered with a chalky layer, 

 but when this layer is removed a pitted surface much like that of 

 this specimen is exposed. The minutest markings of the shell 

 are preserved in the matrix, and in this there is no evidence of 

 any scratches such as usually occur in the chalky layer of the 

 cormorant's egg. It seems improbable that the chalky layer 

 would have been washed off without injury being done to the 

 egg, neither is it probable that it was firmly united with the 

 matrix and pulled away in separating the egg shell from the rock. 



While the specimen much resembles the type egg of the 

 cormorant, it is also very much like the egg of the larger grebes 

 or herons, the American bittern and the limkin. Again, 

 while the ratio of the short to the long axis is somewhat less 

 than that of the typical egg of a duck, it corresponds almost 

 exactly with measured eggs of many of the larger species of this 

 family. It is probable that when this egg was deposited the 

 region was not near to the sea. Under geographic conditions 



