122 TRANSACTIONS OF THE WAGNER FREE 



to the foraminiferal exponent of the Vicksburg beds counts for naught, 

 although in itself the presence in great quantity of an orbitolite would, if 

 not exactly indicate, at least suggest, the Oligocene period. But the 

 genus is also fairly abundant in the periods preceding and succeeding 

 i. e., Eocene and Miocene so that corroborative evidence of one kind or 

 another is needed before we can definitely assign its true position as a 

 constituent of rock masses. Now, it is a significant circumstance that the 

 Oligocene rock proper of the Floridian peninsula that which I have indi- 

 cated as the " Orbitoitic " which is characterized by an abundance of 

 remains of the genera Orbitoides and Nummulites (either of the one or 

 the other, or of both), is wholly wanting in the genus Orbitolites, at least 

 no indications of that genus have as yet come to light there. On the 

 other hand, the genus is represented in the Miocene deposits of the island 

 of Santo Domingo, and by a form which differs but little, if at all, from 

 that which is so abundantly developed in the cream-colored or yellowish 

 limestone of Ballast Point and Magbey's Spring. This form appears to 

 be closely related to, if not identical with, Orbitolites complanata, a well- 

 known fossil of the European Tertiaries, whose range extends from the base 

 of the Eocene possibly to the present time. Again, in the orbitolite rock 

 of the localities just referred to, I failed to detect even as much as a trace 

 of either Nummulites or Orbitoides, a circumstance of no little significance 

 when the proximity of this formation to the recognized Orbitoitic of the 

 North is taken into account. The conjunction of these circumstances leads 

 naturally to the supposition that the rock in question is not a member of 

 the Oligocene series, as has been very generally supposed. Its geographical 

 position, and the fact that the genus Orbitolites is a member of the 

 Dominican fauna, lends strong support toward considering the true 

 age as Miocene, a conclusion which receives further confirmation 

 from the evidence carried by the fossils associated with Orbitolites. 

 These are in most cases in the form of casts and impressions, mainly 

 undeterminable, but a few of them are sufficiently distinct and charac- 

 teristic to permit of definite location. One of these, and possibly the 

 form that is most abundantly represented, is Venus penita, from the 

 casts and impressions of which in this rock the species was originally 

 described by Conrad. This shell figures very prominently among 

 the silicified fossils of Ballast Point, but is, as far as I am aware, entirely 

 wanting in the Cerithium rock of the Hillsboro River, which, as has 

 already been shown, underlies the rock containing Orbitolites. Other 

 species apparently identical with forms occurring in the silex-bearing 

 "marl" of this locality are Cytherea staminca and C. nncifonnis. A large 

 cone, possibly identical with Conus planiceps, is represented by several 

 casts. 



It is to be further remarked, that the Cerithium C. Hillsboroensis 



