REVIEWS Nees 
and, when such, are, in all cases that I examined, chalcedonic silica ; 
the larger ones showing the structure characteristic of chalcedony. . . 
The outside of the nodule is composed of a laver of chalk one-quarter 
to three-quarters of an inch in thickness, cemented with infiltrations of 
silica.” Generally there was only one layer of the chalky substance, 
but in one nodule four alternations of this material with layers of solid 
amorphous silica were observed. 
Preparatory to studying, the flints sections were cut in various parts 
of the nodules and at varying directions, so as to discover if there was 
any difference in the character of preservation, etc. 
The origin of the nodules is assumed to be the same as that of 
those in England and on the European continent, z.¢., “‘that the source 
of these stones is organic silica, and that the principal source of this 
silica is the framework of silicious sponges.” ‘This conclusion is con- 
sidered justified “‘from the great similarity of physical characteristics 
of nodules and surrounding materials in the Cretaceous of Europe and 
America, and also from the fact that the included fossils are of the 
same families and genera.” 
Remains of the following organisms were found: Foraminifera, 
were in every slide, and were represented by Glodigerina and Textul- 
aria. Sponge spicules, were very numerous ; and imperfect remains of 
mollusks and fish scales were present. 
To the condition of the preservation of the sponge spicules con- 
siderable attention is given. They were found in all stages of preserva- 
tion, but excepting the globo-stellates, very few were perfect. Some- 
times numerous faint tracings of spicules merged, so that their outlines 
could not be followed, more often, however, they were separately 
imbedded in amorphous silica. The canal usually showed a separate 
crystallization from the body. Its size varied greatly, sometimes there 
being only a ring of crystalline silica on the outside. The canal may be 
replaced by dark opalescent silica, or it may be hyaline in appearance. 
The globo-stellate spicules were composed, in most cases, of 
amorphous silica, and Mr. Merrill suggests that they may represent the 
colloidal silica originally deposited by the sponge. In these spicules 
evidence was found corroborating the experiments of Sallas, viz., that 
the globo-stellates are dissolved from the center outward. This is 
illustrated in Fig. 22, in which the center portion of the spicule has 
been entirely dissolved and only the spines are left. Some spicules 
were replaced by peroxide of iron. 
