^"'i ^6^'' J Shufeldt, Fossil Birds' Eggs. 83 



gravity of the various kinds of mud, and whether it might or might 

 not contain substances in tlie way of vegetation, stones, &c., 

 which would prevent absohitely an addled egg settling down into 

 it. Addled eggs often float, and the smi and the elements produce 

 marked changes in them if left to their fate, to be tossed about in 

 the water where wind and waves during storms would be almost 

 certain to fracture them sooner or later. Then, the shell of egg 

 and its lining membrane do not form especially favourable septa 

 for the process of osmosis to proceed, and the success of the process 

 would be considerably diminished in the case of a floating, addled 

 egg — a fact that may be readily appreciated. 



When one comes to take all these factors into consideration — 

 with a few others which I have not touched upon — it will be clear 

 that some other view must be advanced as to how the eggs of 

 birds may fossilize. I am of the opinion that the only way in 

 which this can happen is when a more or less recently-laid bird's 

 egg, of medium size, received, in' one way or another, a restricted 

 fracture or puncture of the shell that so far rends the internal 

 lining membrane of the latter as to allow the yolk and albumen 

 of the egg to escape gradually, while their place is taken by other 

 matter, having the nature of a soil, a sand, or mud, which can 

 ultimately undergo the usual process of fossilization. Should the 

 fracture be so extensive as to allow of too easy an ingress and 

 egress of the mud, sand, or earthy matter in which the egg 

 became lodged after its injury, then it would be more than likely 

 that it would be, in its weakened condition, and from one cause 

 or another, more extensively broken up and its egg-shape 

 destroyed. Should this happen — the broken pieces subsequently 

 fossilizing — no one would be able to recognize them in any matrix 

 as being pieces of the shell of an egg of a bird. 



To best insure the future fossilization of the shell of a bird's egg 

 — admitting that the yolk and albumen never fossilize — is to have 

 the aforesaid puncture or fracture received at the butt ; for in 

 that locality the air-chamber of the egg is present, situated 

 between the internal and the external membranes. With the 

 latter ruptured, and an internal, open space at hand, it is evident 

 that the way would be cleared for the easy escape of the contents 

 of the egg, and for the ingress of any soft, earthy constituents, in 

 which the specimen may have l^ecome gradually embedded after 

 the reception of the aforesaid fracture or puncture. The next 

 most favourable point for the latter to be received would be the 

 opposite end of the egg, or at the apex of such eggs as may happen 

 to be more or less pointed. Lateral fractures, of a greater or less 

 extent, though by no means militating against the ultimate 

 fossilization of the shell, are usually more extensive in character, 

 thus rendering the egg liable to l^e still further broken up, or so 

 much crushed that it finally loses entirely the form it originally 

 possessed, and one might or might not recognize it in its matrix 

 as a fossil. 



For very evident reasons, tlic most likely specimens of " fossil 



