PALEONTOLOGY. 287 



Cytherea nuciformin, ]k IIG, iil. xvi, f. (Jl. 



Liiciiia Jlilhboroeiisix, p. 117, pi. xvi, f. 62. 



Crassatella dcfoi'mis, p. 117, pi. xvi, f. (j',i. 



Cardifa (Carditamera) serricosta, p. 117, pi. xvi, f. 04. 



Arcaarcida, p. 118, pi. IC), f. ()5. 



Ledaflexiwsa, j). 110, pi. xvi, f. (iG. 



From north of Ballast Point: 



Cerithium ITiUsboroeii.'iis, p. 124, jtl. viii, f. G7. 

 CerWnum cornntum, p. 124, pi. viii, f. 68. 



Keceut Floridiaii fauna, not fossil: 



Tropidoiiotits iaxispilotus ? var. Brocki, p. 12'J, pi. xvii, f. «, hy c. 

 Ictalurus okeechoheensis, yt. 129, pi. xviii. 

 Aplysia Willcoxi, p. i;?0, pi. xix, f. a, b, c. 



William 11. Dall (58) publishes some interesting notes on the Geol- 

 ogy of Florida, giving accounts of the results of explorations undertaken 

 by instruction of the Director of the U. S. Geological Survey in 1885 

 and 1887. The paper discusses the geological structure and strati- 

 graphical sequence of deposits, and the author refers casually to the 

 occurrence of species of fossils in the deposits studied. " In referring 

 to the age of the deposits," he says, "while the old terms Miocene, 

 Pliocene, etc, may be used for the sake of convenience, it must be 

 clearly understood that, as at present defined, they are only of relative 

 value and indicative at most of stratigraphical succession in a very 

 limited sense. As determined by their invertebrate fauna, the Plio- 

 cene, for instance, of South Europe, is probably older than the strata 

 called Pliocene in America ; at all events it is highly improbable that 

 they represent synchronous geological epochs. The method of determ- 

 ining which name should be used for a particular division of the Tertiary, 

 by taking percentages of the supposed extinct species, is, on the face 

 of it, impracticable, illogical, and misleading. Our knowledge of the 

 Tertiary in America is still so fragmentary and imperfect as to render 

 a synclirouic subdivision of all the Post-Cretaceous strata impossible 

 for the present." 



L. 0. Johnson (132) speaks upon the structure of Florida. Several 

 fossils are identified, indicating Eocene age for the underlying rock (of 

 the Vicksburg group) ; this is covered in places by the " Nummulitic 

 limestone," and upon this rest the Miocene and more recent rocks. 



J. G. Cooper (35, 36) has published lists of California shells in the 

 Proceedings and Bulletins of the California Academy of Science, and 

 the Annual ltei)ort of the State Minei-alogist of California. 



Lester F. Ward (209) presents the evidence as to the age of the Poto- 

 mac formation derived from the study of the work of Professor Fon- 

 taine upon this remarkable ilora. lie tabulates the species, comparing 

 them with those known and descril)e<l from other deposits whose geo- 

 logical position is well known, and " from this exhibit it ap})ears that 

 no Jurassic species occurs in the Potomac formation, although it con- 



