MERRILL: FOSSIL SPONGE SPICULES. 11 
Classification of the Spicules. 
A complete system of classification of fossil sponges was first success- 
fully attempted by Professor Zittel in 1877, on the basis adopted for the 
classification of recent sponges by Oscar Schmidt. Since that time 
much work has been done in England by Messrs. Carter, Sollas, and 
Hinde, and on the Continent by Zittel and various others. As no work 
has been done on the flints of America, I found many forms not figured 
in fossil studies, so that I have been compelled to study the works of 
Schmidt, Bowerbank, Sollas, and Carter, and the Reports of H. М. 5. 
* Challenger ” on recent sponges, in order to locate them. Моге than 
half of the forms studied have never been found fossil before, and I 
have classified them by comparison with both fossil and recent forms. 
Some of them I have been able to locate no further than the family, and 
others to the genus. Some of these forms, especially of the Monactinel- 
lids, I have traced as far as I could with the literature available, but 
have not felt competent without type fossils and more research to sug- 
gest scientific names. However, I have figured them and referred them 
where possible to genera, in the hope that they may be used for reference. 
In the Tetractinellids, the globo-stellates are so widely different from 
anything described or figured, either fossil or recent, that I have thought 
it allowable, and even necessary, to give them specific names, in order 
that they may be referred to more accurately. However, it must be 
remetnbered that every sponge has two or more kinds of spicules, and 
when they are detached, it is a matter of great difficulty to combine 
them with sufficient accuracy for reliable classification. 
I am aware also that the globo-stellates are not considered of much 
value in determining the classification of recent sponges ; but as spicules 
of this type are so prominent in the Texas flint, it is desirable, it seems, 
to name them without regard to the combination of spicules necessary 
to define the species. It is possible that two or more of the spicules to 
which I have given specific names belong to the same species of sponge, 
but this there can be no way of finding out at present. The names 
are therefore proposed in the hope that they may be useful in the study 
of Texas flints. Only the largest and most perfect: spicules have been 
figured, because I hoped thus to get the.adult form, The measurements 
were taken with the utmost care with a micrometer. The classification 
of the orders which follow has been taken from Professor Zittel’s ** Fos- 
sile Spongien," and most of it from the translation by W. 5. Dallas in 
