614 



SIR J. W. DAWSON ON BURROWS AND TRACKS OP 



ciferous formation at St. Anne's, and are similar to markings of this 

 kind which I have described from the Lower Carboniferous of Nova 

 Scotia *. 



Pig. 17. — Butliotrepliis Grantii. A true Eucoid : carbonaceous. 

 Niagara Formation. J nat. size. (Prom a Photograph.) 



§ yill. Kill-marks, as distinguished prom Animal- or Plant- 

 impressions. (Pigs. 18 & 19.) 



In my ' Acadian Geology ' I have described the remarkable appear- 

 ances simulating Algae, or even gigantic trees, produced in the sloping 

 banks of fine mud in the tidal channels of the Bay of Pundy. These 

 are formed by minute rills, oozing from the wet sand or mud, and 

 trickling in fine streams along the slimy surfaces, and uniting into 

 larger and larger streams so as at length to produce the likeness of 

 impressions of flattened trees, with large trunks and branches, divi- 

 ding into twigs of extreme tenirity. Similar surfaces are often 

 found in the Coal-formation, and sometimes on quite as large a scale 

 as in modern tidal estuaries. Their forms and arrangement difi'er 

 according to the slope and character of the sediment, and the amount 

 of water it contains ; but all show very delicate and often regular 

 branching impressions. Pigs. 18 and 19 represent two types of 

 these in my collection from the Carboniferous of Nova Scotia, and 

 * ' Acadian Geology,' p. 256. 



