Die Silurische Farina des Westlichen Tennessee. 191 



many specimens of wliich, on account of the obscurity of their furrows, 

 would otherwise be mistaken for it. It exhibits in its interior, a tex- 

 ture composed of countless little spicula, grouped in the form of stars, 

 entirely analogous with the Astylospongia pr<jemorsa. On the other 

 hand, there are no such large canals radiating from the center, as are 

 to be observed in the other species, and the concentric canals observ- 

 able therein seem to be here altogether wanting. 



General A^ipearance : I have before me fourteen specimens of this 

 species, the smallest of which is of the size of a hazel-nut, and the 

 largest of which is of that of a walnut. Besides the difference in size, 

 these specimens may be distinguished especially in respect to the clear- 

 ness and number of their furrows. Several of these specimens are in 

 jmrt still embedded in pieces of Silurian limestone. The substance of 

 the petrification of all these specimens is as with Adylospongia prcemorsa 

 siliceous. 



Astylospongia inciso-lobata — (Rgemer). 



A round, depressed spheroidal sponge, which is divided with from 

 six to eight deep, incisive furrows, running down over the sides from 

 the top, and reuniting in the center of the under side, forming at the 

 circumference unequal rounded lobes. The texture is everywhere 

 equally compact or finely porous. Larger openings are not to be ob- 

 served, and a surface attachment or epitheca is wanting. Some speci- 

 mens, of a form almost entirely globular, and hardly depressed, with 

 irregular shallow furrows, very much resemble the preceding species ^ 

 and it is possible that both species are connected together by interlink- 

 ing forms or transitions. 



Its inner structure was not observed, and in that far its belonging to 

 that species was left in doubt. On the other hand, the absence of an 

 epitheca is beyond all doubt. 



Of the six specimens before me the largest is an inch in diameter. 

 This is embedded in a piece of hoi-nstone, with which is ingrown at the 

 .>ame time a piece of the calix of an Encalyptocrinus. 



Astylospongia imbricato-articulata — (Rckmer) . 



Incomplete cylindrical, rather thickening toward the top, with its 

 surface covered with ring- formed intervals from top to bottom. The 

 top is concave, and at the bottom of the concavity displays from six to 

 eight larger openings. It is observable from a cross section that these 

 openings are the mouths of pipes, which run through the whole length 



