84 



Bakkr, I lie Swallowinfi of Stones hy .Animals 



n 



ct. Nat. 

 Vol. 73 



In one specimen of which the largest dorsal vertebrae were four inches in 

 diameter, there were at least half a bushel of these stomach stones, ranging 

 from the size of a walnut to four inches across". 



And in a further paper by the same author (1907): "with a Cloasaur 

 skeleton, imbedded in hard concretionary sandstone were found near the 

 forelegs, three rounded, polished, well-worn pebbles, measuring nearly three 

 inches across. Similar stones had not been seen elsewhere in the deposit". 



From the type specimen of Ailantosaurns immanus Marsh, were obtained 

 a number of rounded and highly polished siliceous pebbles ; these were 

 considered to be gastroliths. G. L. Cannon (1906) describing these says, 

 "no material of similar size, form, surface markings or composition, occurs 

 elsewhere in the Atlantosaurus clavs in the vicinity". 



Fig. 2— "Stomach Stones" of Plesiosaur. with portions of the backbone. 



Another record by G. J. Hares (1917) states that "large numbers of 

 gastroliths. some very highly polished, others scarcely polished at all, were 

 found in the Cloverly Formation of the Bighorn Basin, Wyoming, at about 

 the base of Pryor Mountain in Montana, in shales containing animal bones. 

 Some of the stones were over six inches long, and consisted mostly of highly 

 siliceous rocks, jaspers, chalcedony, quartzite, etc. If the highly polished 

 stones are true gastroliths. then it is probably that the unpolished ones are 

 likewise gastroliths". 



Living Reptiles 



Let us turn now to the living reptiles, where there is ample evidence that 

 these still do swallow stones. 



