160 E. M. Kindle — Origin of "Batrachioides the Antiquor ". 



In accepting the conclusion of Hitchcock, that the Lockport and 

 Connecticut sandstone impressions originated in a manner analogous to 

 ' tadpole nests ', it will be necessary to reconsider the questicm of 

 origin of the 'nests'. As already noted, so eminent a naturalist as 

 Alexander Agassiz doubted the ability of tadpoles to produce the 

 impressions ascribed to them. There can, however, be no doubt that 

 tadpoles are sometimes found associated in shallow water with the 

 ' nests ' which have been attributed to them, but the association 

 of the two will not, taken alone, establish a causal relationship 

 between them. The two photographs (PI. VJII, Fig. 2, and 

 PL IX, Fig. 3 ') show the appearance of the structures called 

 ' tadpole nests ' by Hitchcock and others. The photograph (Fig. 2) 

 shows a shallow pool which occupied the bottom of a small 

 abandoned quarry. The writer spent several hours about the 

 sides of this pool collecting fossils. It thus happened tliat 

 abundant opportunity was afforded while cracking open blocks 

 of the adjacent limestone to observe closely the behaviour of the 

 tadpoles associated with these pits. When these observations were 

 made the size of the pond had been reduced by evaporation till it 

 was generally less than 1 foot in depth, and the hundreds of tadpoles 

 in the water were evidently suffering from over-population and 

 reduced food supply. A number of the tadpoles which had died, 

 presumably as a result of this condition, were furnishing food to the 

 survivors. In feeding upon their deceased associates, five or six 

 tadpoles usually attached their mouths to the body of the dead 

 batrachian, and in this way a ring of half a dozen vibrating tails 

 almost constantly surrounded the bodies of each of the victims. 

 During the feeding the movements of the concentrically disposed 

 tadpoles tended to disturb the sediment immediately below. At the 

 time the observations were made the writer believed that the shallow 

 pits had been produced entirely by these activities of the tadpoles. 

 But more recent studies of interference ripples has led him to 

 conclude that the 'nests' ai'e interference ripple-marks slightly 

 modified by the tadpoles. The point may be raised that the photo- 

 graph of interference ripples here reproduced (PI. IX, Fig. 4) shows 

 the pits separated b)^ sharp angular ridges, whereas the ' nests ' have 

 comparatively flat or gently rounded partitions. The writer has 

 found that diiferent examples of interference ripples show a rather 

 wide range of cliaracteristics with respect to this feature. Just as 

 ordinary ripple-marks show crests, which in examples produced 

 under different conditions range from sharply angular to nearly flat 

 or rounded, so interference ripples exhibit corresponding variations 

 of type. Successive observations of one set of interference ripples 

 continued for three days by the writer have also shown that ageing 

 of the impressions under the influence of a shifting direction of 

 the wind tends to alter angular partitions to rounded ones. The 

 comparative rarity of the so-called 'tadpole nests' affords strong 

 evidence that they are the product of the wind rather than of 

 tadpoles. The writer has observed many scores of ponds with tadpoles, 



^ The writer is able to publish this photograph through the courtesy of 

 Mr. G. K. Gilbert. 



