E. M. Kindle — Origin of "Batracliioides the Antiquor ". 161 



but has only once seen the dimpled surface called ' tadpole nests ' by 

 Hitchcock associated with them. Inquiries have been made of 

 a number of zoologists for information concerning the alleged tadpole 

 habit of making nests, but the writer has been able to find no 

 zoologist who was aware that tadpoles ever indulged in such a habit. 

 If such structures were ever produced by tadpoles one might 

 reasonably expect to find them generally associated with these 

 creatures. These considerations, together with the fact that the 

 oscillation of the water under certain conditions of wind action 

 produces structures similar to the so-called 'tadpole nests', lead 

 to the conclusion that those observed hj Hitchcock and others are 

 interference ripple-marks, perliaps slightly modified in outline by 

 tadpoles. 



Comparison of the photograph of the im])ressions on the Niagara 

 Dolomite with the photograph of interference ripples which was made 

 from moulds of interference ripples taken under water at Britannia 

 beach, Ottawa, indicates clearly a similar origin for both. The strong 

 resemblance of the two photographs is such that one can scarcely 

 doubt that they have had an analogous origin. Interference ripples 

 are much less common than the wave-like type of ripple so frequently 

 seen in shallow waters. They are developed under shallow water' in 

 which the ordinary wave generated by the action of the wind on the 

 surface is split up into two or more sets of oscillations moving in 

 different directions. The gradual movement of fine sediments by 

 such conflicting currents, which may proceed so slowly as to be nearly 

 imperceptible to the casual observer, results in the coai'se cell-like 

 structure shown in PI. IX, Fig. 4. The small eddies and cross 

 currents which originate about the ends of bars, piers, or stranded 

 logs are favourable localities for the development of interference 

 ripples. The cast of the interference ripples shown in Fig. 4 was 

 made in water about 6 inches deep, which was protected from any but 

 the lightest wave action by stranded logs on all sides. If the writer's 

 interpretation of the Lockport limestone impressions is correct, they 

 too were formed in shallow waters in which bars probably furnished 

 the special conditions required for the development of interference 

 ripples. 



EXPLANATION OF PLATES VIII AND IX. 



Plate VIII. 



Fig. 1. Dimpled surface on upper beds of Lockport dolomite at Pendleton, 

 N.Y., " Batrachioides the Antiquor " of Hitchcock. 

 ,.2. ' Tadpole nests ' on bottom of shallow pond, Hamilton County, Ind. 



Plate IX. 



,, 3. Photograph of ' tadpole nests ' in small pond. By W. W. Gilbert. 

 ,, 4. Interference ripple-marks. Photograph from mould of cast taken 

 under water at L. Deschenes. 



' The writer's observations have been limited to shallow water, but it is 

 probable that interference ripple-marks would be produced in water of 

 considerable depth where a rocky ledge or other obstruction to normal 

 oscillation of the water generated by wave action extended into a sandy 

 bottom. 



DECADE VI.— VOL. I.— NO. IV. 11 



