SPONGES. 219 



CLASSIFICATION. 



While the methods of investigation demanded by the advanced 

 state of the study of natural science, make a natural classifica- 

 tion possible, they add also very largely to the labors of the 

 investigator. This is especially true of the student of palaeozoic 

 sponges, not only because the fossils of this class preserve so 

 little of their structural details, but also because these early 

 forms are ancestral types in which the characters, that in 

 Mesozoic and more recent times have been separately developed 

 into permanent structural characteristics, are as yet illy defined 

 and generally blended together. The commingling of subse- 

 quently differentiated characters, even with the best preserva- 

 tion, imparts a degree of uncertainty to many of our determi- 

 nations, but as we have in every instance sought to work out 

 the minute structure as fully as the state of preservation of the 

 fossils would admit, we hope the authorities on the subject will 

 not take our views too much to task when they find it neces- 

 sary to differ with us. 



It is not deemed essential to refer to the classifications of D'Or- 

 bigny, Fromentel, and others, beyond stating that all have 

 proven utterly inadequate because of their artificial character. 

 This is clearly shown by the heterogeneous composition of the 

 groups proposed in their systems. To Prof. Zittel belongs the 

 honor of discovering the principle of a natural classification for 

 fossil sponges. He accepts as the fundamental basis of his sys- 

 tem the characters of the minute spicular bodies of which the 

 sponge skeleton is composed. The validity of the system has 

 already demonstrated itself by the excellent results of its appli- 

 cation, since, where we formerly had a chaotic intermingling of 

 distinct types, we now find the most harmonious arrangement. 



According to the classification proposed by Prof. Zittel*, and 

 adopted by Dr. Hindet, and others, the Class SPONGLE is 

 divided into the following Orders: 



* "Studien uber fossile Spongien" I. II, in, Abh. d. Bay. Akad. d. Wiss. Bd. 13. 1877- 

 78, and "Handbuch der Palasontologie." 



t Catalogue Foss. Sponges, British Museum, 1883, 



