404 



University of California. 



[Vol. 3. 



gravels on the Gila River in Arizona. Mr. Helmore being 

 unwilling to part with the specimen has kindly loaned it to the 

 University for study and description. 



When found, the egg formed the center of a rounded mass of 

 hard calcareous rock which may be called the capsule. The 

 surrounding matrix had been, partly removed and the egg broken 

 open before it came into our possession. As it was necessary to 

 obtain a fresh unrubbed surface of the shell for study, the 

 enclosing rock was removed in the laboratory. 



Since this seems to be a unique specimen it has been thought 

 advisable to put the principal facts concerning its preservation 

 on record. The authors are indebted to Professor Merriam for 

 many suggestions during the course of this study. 



OCCURRENCE. 



Unfortunately, the information which we have concerning the 

 occurrence of this specimen does not give us very definite evi- 

 dence concerning its age. The encapsuled egg is said to have 

 been a pebble in gravels some distance above the present level of 

 the river. If, as has been supposed, the gravels are bench 

 deposits, the egg is at least as old as the Quaternary. If they 

 are of Recent origin we can still hardly suppose it younger than 

 Quaternary, as it is only under the most extraordinary circum- 

 stance that deposits of Recent origin can occur as hard pebbles in 

 Recent conglomerates. 



THE ENCLOSING CAPSULE. 



The nature of the capsule when the specimen was first exam- 

 ined is shown in Plate 48, figures 2 and 4. Some of the matrix 

 had been removed at that time. The enclosing rock forms a 

 flattened ellipsoid measuring about 3^X4X5 inches. The surface 

 was sharply ridged, due apparently to differential weathering of 

 the thin layers of matrix. The greater part of the matrix is highly 

 calcareous and might be designated as limestone. The outer 

 layer is of finely laminated clay. 



When the capsule was removed its inner surface was seen to 

 be marked with peculiar pits (PI. 48, figs. 3 and 4), and to be 

 covered with a very thin film of a tarry material, which usually 



