20 E. H. SELLARDS 



one formation to another. That the extinct turtles do not repre- 

 sent inclusions from the older formation is evident by the fact that 

 practically complete carapaces are found, which in some instances 

 are so delicate as not to stand so much as turning over without being 

 broken. That the mammals referred to No. 3 are normal to that 

 deposit is indicated both by the abundance of the bones and by 

 their condition of preservation. 



INTERPRETATION OF THE SECTION 



It is desirable in this connection to consider the interpretation 

 of the section as a whole, especially as to whether or not an appre- 

 ciable period of time intervened between the deposition of divisions 

 1 and 2 of the section, and also between divisions 2 and 3. As a 

 rule, it is possible to recognize the dividing line between the marine 

 stratum, No. 1, and the fresh-water deposit, No. 2. At such places, 

 even though the marine shells are lacking in No. 1, there is a 

 change in the texture, and usually also in the color, of the sand. 

 Moreover, one finds rather commonly irregularities at the top of 

 No. 1, which are due to stream wash. Occasionally there are also 

 depressions or holes in the top of No. 1. Such holes, so far as 

 observed, as previously stated in this paper, contain muck and 

 decayed wood and sticks. However, notwithstanding this appar- 

 ently well-marked break, there are other places where the dividing 

 line between Nos. 1 and 2 is evident neither by the change of 

 texture of the sand nor by any change in color. At such places 

 deposition appears to have been continuous from stratum No. 1 

 into stratum No. 2. On the other hand, there is at all places 

 evidence of the change from marine to fresh-water deposition. 

 Since the fossils of No. 1 are marine, while those of No. 2 are land 

 forms, there is little opportunity of connecting the two divisions 

 by means of the fauna. Aside from the one camel bone obtained 

 at West Palm Beach, no land animals are known from No. 1 of this 

 section. 



In the preceding papers the writer has commented upon the 

 abrupt break which normally exists between strata Nos. 2 and 3, 

 a break which it seemed possible might be taken to indicate a con- 

 siderable interval of time. The later observations of this section, 



