34 Die Silurische Fauna des Wedlicheii Tennessee. 



the original place of deposit of the species, it can no longer be doubted 

 that the specimens which occur in Europe also have their origin in 

 these strata. All the specimens found in the diluvium of the North 

 German plain, in so many j^laces, certainly come from the destroyed 

 Silurian strata of Northern Europe, and, indeed, from the Upper Si- 

 lurian strata of the age of the limestone strata of the Island of Goth- 

 land, which are contemporaneous with those of Tennessee. As a mat- 

 ter of fact the Gothland species is frequently and manifestly found in 

 the original place of deposit. I have seen in the Gymnasium Collec- 

 tion at Wisby beautiful specimens, as large as apples, and \ myself 

 picked up one from the strand at Wisby. Finally, the Berlin Museum 

 (and this is decisive), possesses specimens from Wisby, which are still 

 embedded in Silurian limestone. In the University Collection, in 

 Christiania, I have this year seen a sponge, coming from the dark blue 

 Silurian limestone of that region, which I, although it is only imper- 

 fectly preserved, ascribe to our species. 



Siphonia excavata is synonymous with Astylospongia prcemorsa. This 

 species was created l)y Goldfuss from a single specimen from the Bonn 

 Museum, which differs from the original sjiecimen of the Siphonia 

 prcemorsa only by a deeper excavation of the crown, coming from dis- 

 integration. The peculiar, concentrically Avrinkled coating of the under 

 .side (similar to the epitheca of some anthozoa, but occurring also in 

 other fossil .sponges), which the specimen exhibits, I have observed in 

 another specimen of the Siphonia j}roemorsa, from the Island of Goth- 

 land, If, therefore, these two species are to be united into one, this 

 latter must receive the name Astylospongia pnemorsa, because this name 

 Avas given to the species in the condition of perfect preservation, while 

 the name SipJtonia excavata was given to a disintegrated specimen. So, 

 also, Hisinger's Siphonia stlpitata is evidently, from the ' drawing and 

 description, not a different species, but merely a specimen in which the 

 concave crown is covered with an accidental, conically projecting 

 appendage of silica. The statement of D'Orbiguy (pro drome ii., page 

 286), who calls the species Jerea excavata, and says that it is found in* 

 the chalk of Maestricht, is just as erroneous as manj' other statements 

 of that author in regard to the places where, outside of France, fossils 

 are found. 



Note. — The above description of the genus Astijlospongia, and the 

 species A. prcemorsa, seems to be confined to siliceous sponges ; but 

 -other naturalists are of the opinion that they may be calcareous — 

 that the fossilization, Avhether siliceous or calcareous, depended upon 

 whether the infiltrating water held silica or lime in solution, and not. 

 njjon the constitution of the sponge while living. One thing is cer- 



