26 TRANSACTIONS OF THE WAGNER FREE 



concealed along the deeper and inaccessible parts of the stream. In the 

 everglade tract above Fort Thompson two species of Planorbis (P. trii'oli'is 

 and P. \_Physd\ scalaris), besides the large Ampullaria, were very plentiful, 

 and still nearer the interior lakes the dredge brought up quantities of one 

 or more species of Vivipara (V. lineata, V. Gcorgiana .'). 



GEOLOGICAL FEATURES OF THE CALOOSAHATCHIE. The banks of the 

 river for its entire course are very low, at no place probably rising much 

 above twelve feet. They are highest in the middle and upper course of 

 the stream, where their faces are cut down almost vertically to the 

 water's level, below which they descend at a very steep angle. In the 

 lower reaches of the river they barely attain one-half this height, and, 

 indeed, for a very considerable distance above Fort Myers, the average 

 elevation probably does not exceed three or four feet, and beyond the 

 immediate border the land-surface, showing unmistakable signs of 

 periodic overflows, sinks still lower.* Compact rock crops out here and 

 there, or may be seen lying in the channel, but for by far the greater 

 distance the banks consist of a partially indurated marl, in which, at 

 places, fossils are exceedingly abundant. In my experience I have never 

 met with an exposure in which fossils were nearly as plentiful as in the 

 vertical cut which extends almost uninterruptedly for ten or more miles 

 below the Thompson rapids. Fosrils could here be counted by the 

 million, and were as densely packed, but without crushing, as it was 

 possible for them to have been placed together. Their state of preser- 

 vation was also wonderful. 



Owing to the innumerable turns in the river, and the fact that the beds 

 exposed maintain a well-defined horizontality for most of their extent, 

 I was unable to satisfy myself as to the direction of true dipt, so that 

 it may yet be an open question how much of the more westerly exposed 

 rocks, or those cropping out at, and immediately above, Fort Myers, cor- 

 respond to the rocks exposed along the upper stream. The fact, 

 however, that there is such a slight difference in level between the inner 

 and outer points, and the circumstance that for such a long distance the 

 practical horizontality of the beds can be connectedly followed, lead me 

 to suppose that the entire system is in reality one, despite a certain 

 amount of variation both in the lithological and faunal features of the 

 deposits. 



* Tide-water, or perhaps more properly back-water, is said to extend to Fort Thomp- 

 son. We, however, found a strong river-current for a considerable distance below this 

 point, both during our ascent and descent of the river. The difference between mean high 

 water and mean low water at Fort Myers has been determined by Meigs to be 2.2 feet. 



t At one point, not very far above Daniels', the strata show a decided declination to the 

 east, or towards the interior of the State, but I feel confident that this marked deviation from 

 the horizontal is a local circumstance, and has but little bearing on the question of true dip. 



