Revieus — Dr. G. J. Hinders Fossil Sponges. 133 



pared and polished block added to the Temple of Science, to the 

 building up of which so many earnest workers have devoted their 

 lives. 



The group of organisms which form the subject of the present 

 ■volume had, owing to their obscurity, been only impei'fectly worked 

 out or understood in this country by Toulmin Smith, Man tell, Phillips, 

 Sowerby, Benett, but they have in later years been more ably treated 

 by Bowerbank, Carter, and Sollas ; and the works of Goldfuss, 

 Eoemer, Michelin, Quenstedt, Keuss, Geinitz, de Loriol, Fromentel 

 and especially those of Professor Dr. Karl Zittel, attest the interest 

 taken in this class amongst continental paleeontologists. 



A more intimate and careful study of the Spongida in the past 

 fifteen years has led most observers to the conviction, that in this 

 primitive group of animals, mere external form is insufficient to 

 enable one to speak defiuitel}', at least, of a great many of the fossil 

 genera. Certain forms, like Ccelopfychium, Peronella, Ventriculites, 

 Craticularia, seem definite enough ; but we are by no means sure 

 that even these can always be determined by external form alone, 

 without recourse to the microsco[)e, 



"The classification of the Sponges (writes Dr. Hinde), recent as 

 well as fossil,, rests upan the characters of their skeletal structures. 

 The existing forms of the class have been divided into the following 

 orders : — 



" 1. Mtxospongi^, HaeckeL 

 " Sponges destitute of a solid skeleton. 



"2. Ceratospongi^, Bronn. 

 " Sponges with skeletons of horny fibres. 



" 3. MoNACTINELLIDiE, Zittel. 



" Sponges with skeletons of horny fibres, with cores of uniaxial 

 siliceous spicules, or built up wholly of uniaxial siliceous spicules. 



" 4. Tetractinbllid^, Marshall. 



" Sponges with skeletons of siliceous spicules, usually with four 

 rays or arms, one generally elongated to form a shaft, the other three 

 disposed in a pyramidal form ^ uniaxial and star-shaped spicules are 

 also present. 



" 5. LiTHiSTiD^, 0. Schmidt. 



" Sponges with skeletons of siliceous spicules, either four-rayed, 

 or irregular in form, which are intimately interwoven together into 

 a continuous mesh, 



" 6, Hexactinellid^, 0. Schmidt. 



" Sponges with skeletons of six-rayed siliceous spicules, either 

 loosely interwoven together, or organically united to form a 

 continuous mesh. 



