CONTRIBUTIONS TO PAL^ONTOLOGT. 



69 



Receptaculites oweni, Hall: 



iowensis, Owen: 

 fungosus, 'H.AhL: 

 orbicularis, . . 



Galena limestone. 



zn 



o 



occidentalis* Salter: Trenton limestone. 



The species in tlie Leadbearing limestone of the Northwest, particularly 

 the R. oweni, have the widest geographical range of any known to me. The 

 species in the Niagara group appear to have very limited geographical range, 

 and are of comparatively rare occurrence. Those of the Lower Helderberg 

 group, and Schoharie grit, are known to me only within a very moderately 

 extended area. 



It is probable, however, that these fossils, which are often not conspi- 

 cuous, and which sometimes appear like worn or weathered corals, have not 

 attracted the attention of collectors. Still I am much inclined to the opi- 

 nion that they will rarely be found to have a wide geographical range, and 

 that only at distant points have the conditions been favorable for their full 

 development. Under certain circumstances, some species have been very 

 prolific ; and in the limestone of Iowa, at the junction of the Trenton beds 

 proper with the Leadbearing limestone, the thin layers of rock are some- 

 times crowded with the broad discs of R. oweni, while in a locality near 

 Dubuque the R. iowensis is crowded together in great numbers. 



5. NOTE ON THE OCCURRENCE OF ASTYLOSPONGIA IN THE 

 LOWER HELDERBERG ROCKS. 



In the very beautiful and valuable contribution to American 

 Palaeontology, "Die Silurische Fauna des Westlichen Tennessee," 

 Dr. RcEMER has described six species of Spongi^ from the Silurian 

 strata of Tennessee. These are the ^stylospongia prcemoj'saj A. 

 stellatim-sulcata^ A.inciso-lohata^ AAmhricato-articulata^ PalcBomanon 

 cratera^ Astrceospongla meniscus. All of these species I have had 

 in my collections from Tennessee since 1850. 



The A. prcRmorsa likewise occurs in Europe, and therefore has 

 a wide geographical distribution. Notwithstanding the common 

 occurrence of several of these species in Tennessee, together with 

 Caryocrinus and other fossils of the age of the Niagara group, I 

 have not seen a specimen of either species in the rocks, nor in any 



* I have still some doubt whether the one which I referred to R. neptuni may be 

 identical with this species of Mr. Salter. 



