A CHAT WITH PEOF. COPE — CONTINUED. 355 



by the union of the ribs with bone deposited in the 

 skin. In the very young tortoise the ribs are sepa- 

 rate as in other animals ; as they grow older they 

 begin to expand at the upper side of the upper end, 

 and, with increased age, the expansion extends 

 throughout the length. The ribs first come in con- 

 tact where the process commences, and in the land- 

 tortoise they are united to the end. In the sea-turtle, 

 the union ceases a little above the ends. The 

 fragments of the Protostega were seen by one of the 

 men projecting from a ledge of a low bluff. Their 

 thinness and the distance to which they were traced 

 excited my curiosity, and I straightway attacked the 

 bank with the pick. After several square feet of rock 

 had been removed, we cleared up one floor, and 

 found ourselves well repaid. Many long slender 

 pieces, of two inches in width, lay upon the ledge. 

 They were evidently ribs, with the usual heads, but 

 behind each head was a plate like the flattened bowl 

 of a huge spoon placed crosswise. Beneath these 

 stretched two broad plates two feet in width, and 

 no thicker than binders' board. The edges were 

 fingered, and the surface hard and smooth. All this 

 was quite new among fully grown animals, and we at 

 once determined that more ground must be explored, 

 for further light. After picking away the bank and 

 carving the soft rock, new masses of strange bones 

 were disclosed. Some bones of a large paddle were 

 recognized, and a leg bone. The shoulder-blade of a 

 huge tortoise came next, and further examination 

 showed that we had stumbled on the burial-place of one 

 if the largest species of sea-turtle yet known. The sin- 



