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. Cartel 1 , 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. M. S. 

 " Challenger " on recent sponges, in order to locate them. More 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 

 remembered 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. S. Dallas in 



