66 



SCIENCE 



[N. S. Vol. XXV. No. 628 



DISCUSSION AND CORRESPONDENCE 



GASTROLITHS 



In extension of a recent note by Mr. Geo. 

 L. Cannon on the occurrence in southern 

 Wyoming and Colorado of sauropodan gastro- 

 liths^ similar to those first reported by me 

 from the Big Horn Mountains/ I wish to state 

 that a recent search through the Tale collec- 

 tions has not revealed any further examples 

 directly associated with Dinosauria. 



Meanwhile, however, I have been shown, by 

 Mr. Barnum Brown, four additional speci- 

 mens obtained in Colorado in proximity to 

 various dinosaur skeletons. These gastroliths 

 are very highly polished, and it is noteworthy 

 that one of them contains a fine bryozoan and 

 traces of other marine organisms identically 

 similar to those noted in one of the examples 

 from the Big Horn Mountains. In fact these 

 specimens are so entirely similar in both tex- 

 ture and the fossils contained as to make it 

 quite certain they were derived from the same 

 source, namely, a marine formation contain- 

 ing siliceous nodules in much the same man- 

 ner as the English chalk cliffs — or to cite a 

 somewhat different instance, certain moss 

 agate-bearing carboniferous terranes of the 

 Laramie Mountains. 



Nor is it improbable that the original source 

 of these fossil pebbles may soon be found, and 

 thus still more closely locate the actual hab- 

 itat and haunts of the sauropods. At least it 

 already appears that the dinosaurs of the Big 

 Horn and Colorado localities either picked up 

 the fossiliferous nodules on the same ancient 

 shore line, or else from streams which cut this 

 line along some inland range of hills or moun- 

 tains and carried the pebbles forward into the 

 lower river courses. In the latter and more 

 probable case the dinosaurs would have found 

 the transported fossil bearing pebbles inter- 

 mingled with a variety of others just as in 

 the two occurrences now observed. 



It should be definitely stated that the dino- 

 saurian gastroliths are unmistakable objects. 

 Pebbles which are merely waterworn rarely 



'Science, N. S., Vol. XXIV., No. 604, p. 116, 

 July 27, 1906. 



'Ibid., Vol. XXni., No. 595, pp. 819-821, May 

 25, 1906. 



have other than ground glass surfaces, and 

 where a partial polish approaching a sheen is 

 present, this does not markedly extend into 

 depressions, and is much interrupted by vari- 

 ous irregularities. So also the wind-worn 

 pebbles of steppes, although I have seen near 

 the glacial ice sheet limit of eastern Nebraska 

 large boulders of Sioux quartzite presenting 

 small polished areas due to seolian action; 

 while in the case of the readily determinable 

 desert patina the glassy surfaces are of a some- 

 what different origin. But from all these the 

 dinosaurian gastroliths will never fail of 

 recognition. Except for the original inequali- 

 ties of the pebble outline, though even these 

 may be nearly eliminated, their entire surface 

 may exhibit a higher polish than wind or 

 water ever produces. Indeed the smoothness 

 and sheen are, I may say, from my section 

 making, such as is difiicult to equal, and best 

 compared to the finest results obtained by the 

 use of the buffing wheel. 



It is evident that the dinosaurs were more 

 or less given to selecting the pebbles they 

 swallowed, choosing the brighter colored ones, 

 much as do the ostriches and other birds. 

 And it appears that pebble-swallowing is quite 

 widely characteristic of not only reptiles and 

 birds, but occasionally of other vertebrates. 

 The fur seal, a mammal of ' strong instincts, 

 but little intelligence,' and with shore habits 

 perchance not utterly dissimilar from those 

 of the ancient pebble-swallowing plesiosaurs, 

 as stated by Lucas, quite frequently swallows 

 among other objects pieces of lava, and chalce- 

 dony pebbles, with apparently more or less 

 choice." In none of these other instances, so 

 far as yet known to me, however, are the 

 pebbles long retained and subjected to the high 

 polish seen in the case of the dinosaurs. 

 Strong in gastric secretion, the sauropods 

 perchance sometimes ate, in addition to more 

 succulent plants, primitive or xerophyllous 

 grasses containing considerable silex. But as 

 the gastrolithic habit was doubtless widely 

 characteristic of the entire dinosaurian group, 

 the gastroliths of carnivorous forms will prob- 

 ably be determined, and the degree of attritive 



' ' The Fur Seal and Fur Seal Islands of the 

 North Pacific Ocean,' Part III., page 68. 



