INSTITUTE OF SCIENCE, PHILADELPHIA. 



59 



formation is almost positive indication as to the Eocene or Oligocene age 

 of that formation, and the more especially when the remains of these 

 organisms occur in any abundance. Admitting the supposition of this 

 age, we should naturally look to the associated fossils for further confirm- 

 atory evidence bearing on this point. Singularly enough, in the case of 

 the Florida nummulitic rocks at least in the fragments that have been 

 placed at my disposal with very few exceptions all the molluscan 

 remains belong to a period much more recent than the Eocene, and to 

 species that are still living at the present day. And what may appear still 

 more singular, they are referable in principal part to land and fresh-water 

 genera, Glandina, Paludina, Ampullaria.* From this association and the 

 circumstance that nummulites are still met with in existing seas.it might 

 readily be inferred that there has been here a commingling of contempo- 

 raneous marine and fresh-water organisms, and that the deposits in question 

 were laid down under such conditions proximity to the mouth of a river 

 where a commingling of this kind could take place. Indeed, it would 

 be difficult from paleontological evidence alone to disprove such an 

 assumption, were it not that almost incontrovertible proof to the con- 

 trary, in addition to that furnished by the abundance of nummulites, is 

 afforded in the presence of the remains of Orbitoides, a genus which 

 attained its greatest development in the Upper Eocene (" Nummulitic ") 

 and Oligocene periods, and which does not appear to have survived the 

 Miocene. There can, therefore, be little or no doubt that the rock 

 fragments marked by this admixture of an older and a newer 

 (Post-Pliocene or recent) fauna, and comprising both marine and 

 fresh-water types of organisms, have derived their faunal character in 

 great part from the dep*osits of a more ancient formation, which formation 

 represents, and is the equivalent of, a portion of the European " Nummu- 

 litic " (whether Eocene or Oligocene). The exact locality (or localities) 

 which these Florida nummulitic deposits occupy in situ has not yet been 

 ascertained, but it is fair to assume that the beds lie along the Gulf 

 border (possibly in great part submerged), where, through the disinte- 

 grating action of the oceanic surf, their fragments have at a comparatively 

 recent period been washed together with the material that at the same 

 time was being carried out by the fresh-water streams. The precise 

 position which the formation holds in the nummulitic scale, as fixed by 

 Hantken or La Harpe (Iitiidfn snr Ics Nummulites du Couitc dc Nice, Bull, 

 de la Soc. Vaud. des Sc. Nat., vol. xvi, pp. 223-24, 1879), cannot be posi- 

 tively determined from our present data, since exceptionally the group of 

 the Nnininnliti's plicatee is represented as well in the oldest as in the newest 

 of the Tertiary deposits marked by the members of this class of organisms." 



* The species identified with recent forms are Clandina parallela, Paltidina {Vivipara) 

 W'altonii, and Ampul/aria deprcssa. 



