INSTITUTE OF SCIENCE, PHILADELPHIA. 



*Pecten nucleus, Ostrea meridionalis, 



Anomia Ruffini, * " Virginica. 



Recent species are preceded by an asterisk ; the new species are italicized. 



It will thus be seen that the relation of recent to extinct species is as 

 48 to 41, giving a very much higher percentage for living forms than 

 obtains in any of the divisions of our recognized Miocene deposits, even 

 the " Carolinian," which holds a position nearly equivalent to the so-called 

 Mio-Pliocene of Europe. It becomes manifest that this most extensive 

 Floridian exposure represents the Pliocene age a circumstance interest- 

 ing, apart from the general bearing which its presence has upon the 

 geology of the State in particular, from the fact that it gives us the 

 first unequivocal indication of the existence of marine Pliocene deposits 

 in the United States east of the Pacific slope. 



I made a careful examination of the banks to ascertain if any dividing 

 lines or horizons, characterized by distinct assemblages of organic 

 remains, existed, but failed to discover any such ; the fossils appeared to 

 be packed almost indiscriminately, and in several instances when I thought 

 that a certain localization in some species could be detected, the same 

 forms would appear in other parts of the bank, and completely vitiate all 

 my surmises. Only along the top line was there a true differentiation, 

 the uppermost (marine) bed being densely charged with the valves of 

 Venus canccllata, largely to the exclusion of the numerous other forms 

 that so eminently serve to define the bank in general. Nor did I succeed 

 in obtaining any extinct species from this topmost stratum, although no 

 true junction line between -it and the stratum immediately underlying 

 could be determined. There is no question in my mind that this upper 

 Venus bed, the same as we found it at other points of the river, is of 

 Post-Pliocene age, continuous sedimentation, however, uniting it with 

 the older Pliocene deposits beneath, and obscuring all well-defined faunal 

 lines of separation. 



From the observations that have thus far been made respecting the 

 geology of the State, it will be seen that the Tertiary formations follow one 

 another through the peninsula in regular succession from north to south, 

 beginning with the Oligocene (or late Eocene) and ending with the 

 Pliocene. The Post-Pliocene, doubtless, follows as a continuation of the 

 Pliocene south of the Caloosahatchie, probably for a very considerable 

 distance into the everglade region, and possibly nearly to its end. Our 

 observations failed to bring forward a single fact confirmatory of a coral- 

 reef theory of the formation of the peninsula such as had been advocated 

 by Louis Agassiz and Prof. Le Conte ; on the contrary, the existence of 

 the heavy fossiliferous deposits about Tampa, on the Manatee, along the 



