Die S'diirische Fauna des WestUchen Tennessee. 31 



ing specimens of Astylospongia pi'cemorsa (^Siphonia prcemorsa, Gold- 

 fuss) is there a trace of an epitheca to be seen, but in all of them the 

 semi-circular under side is regularly rounded, without any interruption. 

 So, also, the hundreds of specimens of the remarkable Asinwspongia 

 meniscus are on their flat underside quite smooth, with no scar or pro- 

 jection whatever which could be regarded as an epitheca. Ail these, 

 bodies must have lived free at the bottom of the sea, with the excep- 

 tion, perhaps, of there being partially sunk in sand or slime. All 

 other sponges from the paleozoic strata, that have thus far been discov- 

 ered, also exhibit the same peculiarity, particularly the apple-formed 

 Aulocopium species, which Oswald has described from tlie Silurian dilu- 

 vial bowlders of Sadewitz, near Oels, and a still undescribed sponge, 

 about the size of a man's hand, of a thick disk form, notched on the 

 edge, that is found at Sadewitz, and in the Island of Gothland. Hence, 

 it seems that, in general, all sponges of the first period^ in striking con- 

 trast with the sponges of later formations, and of the present time, xoere 

 free. If, on the whole, in all the lower classes of animals, we regard 

 the stationary condition as a sign of a lower grade of organization than 

 the free condition, the above fact is all the more remarkable for the 

 reason, that, having in view the general indisputable perfection of or- 

 ganisms with the rising gradation of the sedimentary rocks, we should 

 expect just the opposite to be the case. Moreover, the regularity in 

 form of the Silurian sponges, as more particularly manifested in the 

 Adylospongia prcemorsa, and Astrceospongia yneniscus, is evidently depen- 

 dent on this free condition, for we know that in general, in the lower 

 classes of animals, the freer forms have greater regularity of shape 

 than the stationary ones, wherein the size and form of the epitheca 

 partially determines the form of the body. 



Several yeai's ago I gave an enumeration of the sjjonges now to be 



described, in Von Leonhard's & Bronn's Jahrbuch fiir Mineraloo:ie. 



Here the description of them is given more completely and enlarged, 



especially by the knowledge of the interior structure of several species. 



Genus Astylospongia (Dr. Ferd. Roemer). 



This globular, or thick, disk-formed, and almost regularl}^ circular 

 sponge is free, not attached. The inner texture is formed by little, 

 very regular, star-shaped bodies, which are connected with each other 

 by their rays. Larger canals run from the center, in the form of rays, 

 to the surface, and are crossed by concentric canals. Even during 

 the life of the animal the body must have been of a toleral)ly com- 

 pact nature, inasmuch as it is never found compressed. The petrifac- 

 tion is always siliceous. 



The typical species of this genus has been known for some time 



