Morgan and Tattmon — Occurrence of Bitumen. 363 



Art. XXXIX. — A Peculiar Occurrence of Bitumen and Evi- 

 dence as to its Origin; by Wm. Congee Morgan and 

 Marion Clover Tallmon. (With Plates XVIII and XIX.) 



Summary. 

 The following is a description and an account of the exam- 

 ination of a fossil egg from Arizona. When discovered it was 

 enclosed in a limestone matrix which has kept the specimen in 

 a very fine state of preservation. Crystallized colemanite and 

 a tarry material resembling natural asphalts are found within 

 the eggshell. All the evidence which can be collected from 

 the specimen indicates that the asphalt-like substance is part 

 of the original contents of the egg which has become bitumized. 



Introduction. 



Very few instances of the occurrence of eggs in the fossil 

 state have been recorded. The fossil eggs of New Zealand 

 birds are only shells which have been preserved by reason of 

 their thickness and strength. The Chelonian eggs of Tertiary 

 age from Auvergne, France, are simply shells filled, with har- 

 dened mud. An interesting fossil egg from the American 

 Miocene has been described by Mr. Oliver C. Farrington,* and 

 has been considered the egg of a duck. 



The specimen described in this paper was brought to the 

 attention of Professor John C. Merriam some months ago by 

 Mr. G-. A. Helmore of San Francisco. It had been in Mr. 

 Helmore's possession for some years, and was obtained by him 

 from a prospector who found it in a large pebble embedded in 

 placer gravels on the Gila River in Arizona. Mr. Helmore, 

 being unwilling to part with the specimen, has kindly loaned 

 it to the University of California for study and description. 

 To Professor Merriam the authors wish to acknowledge their 

 indebtedness for valuable suggestions during the course of the 

 work. 



Occurrence. 



Unfortunately, the information which we have concerning 

 the occurrence of this specimen does not give us very definite 

 evidence 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 extra- 

 ordinary circumstance that deposits of recent origin can occur 

 as hard pebbles in recent conglomerates. 



* Field Columbian Museum, Pub. 35, vol. i, No. 5, Geological Series. A 

 Fossil Egg from South Dakota. 



