246 The American Naturalist. [March, 
tebrates is developed from the ectoderm and in the development of the 
nephridia “as a rule the ciliated funnel which was present during 
development, becomes completely closed.” P. 85. Between the ecto- 
derm and the entoderm of the sponges “is a gelatinous layer, the mes- 
oglea, amongst the cells of which crystals of lime salts occur,” which 
we suppose to be the spicules, silicious as well as calcareous, of these 
organisms. P. 83. The animal kingdom is divided into Protozoa, and 
Invertebrate and Vertebrate Mesozoa. The Invertebrates are defined 
as follows: “ They possess no backbone, the nerve cord or nerve cords 
are never dorsal, . . . and the heart is always placed in the dorsal 
region.” The Invertebrata are subdivided into Ceelenterata and Cœ- 
lomata, but never a word that the Plathelminthes are not Ceelomata 
and that the vertebrates are. But enough. The work is well illustra- 
ted, mostly by cuts from Claus, Sachs, Prantl and other recent text- 
books. 
Correlation Papers of the U. S. Geological Survey 
Neocene.*—This memoir is the fifth of a series, having been pre- 
ceded by essays on the Carboniferous and Devonian by Mr. Williams, 
on the Cambrian by Mr. Walcott, on the Cretaceous by Mr. White, 
and on the Eocene by Mr. Clark. To an excellent summary of pub- 
lished material on the subject discussed the authors have added 
important original matter based on personal investigations by Mr. Dall 
in the field and laboratory. The following is an outline of the memoir 
as given in the introduction: 
“ This paper, after discussing general principles connected with the 
study and description of the Tertiary or Cenozoic rocks and fossils 
contained in them, takes up the Neocene deposits of the United States 
in particular. 
“ A chapter is devoted to a summary of what is known in regard to 
the Neocene of the eastern coast of the United States, each State in 
geographical order being separately considered, beginning at the north. 
The State of Florida, in regard to which much unpublished informa- 
tion was available, being entirely composed of Cenozoic rocks, and 
therefore as a type of such structure peculiarly interesting, is treated 
of in greater detail and at more length than in other cases. The part 
of this essay relating to the State of Florida is really a preliminary 
geological report on that State, of which the structure has hitherto 
been very little known. The important fact that until the Pliocene 
‘Bulletin of the United States Geological Survey No. 84. Correlation 
Papers—Neocene, By W. H. Dall and G. D. Harris. Washington, 1892. 
