GEOLOGICAL SOCIETY OF PENNSYLVANIA. 



329 



Sequasha valley ; Alabama, Mount Saiio ; Kentucky, 

 between Springfield and Nashville, Tennessee. 



3. P. florealis, Say. Tennessee, Jasper, Sequache 

 valley, between Sparta and Crab Orchard, rare in the 

 limestone near Nashville ; Alabama, Mount Sane, abun- 

 dant; in several places on the base of the different spurs 

 of the Cumberland mountains, Kentucky, between Spring- 

 field and Nashville ; and, according to Mr Say, also on 

 the margins of the Mississippi. 



4. P. ovalis, Goldfuss. Transition limestone at Crom- 

 ford near Ratingen, Dusseldorf, Europe. 



5. P. derbensis, Sowerby. Zool. Journ. vol. 2, 

 page 317, pi. 2, fig. 3. 



6. P. ellipticus. Ibid., page 318. Encrenites Go- 

 doni, Defr. Diet, des Sc. Nat., torn. 14, page 467. 



7. P. Reinwardtii nobis. 



The figure given by Dr Goldfuss of the P. florealis, 

 tab. 4, fig. is an excellent representation of the fossil. 

 The largest specimen in our cabinet of that species is 

 from Cumberland mountain, it is one inch long and seven- 

 tenths of an inch wide. A specimen of the P. globosa in 

 our possession discovered in Illinois, is one inch high and 

 one inch wide. P. pyriformis, of which I subjoin a figure, 

 pi. 10, fig. 8, was found on the western base of the Cum- 

 berland mountains, in Warren county ; it is represented 

 in its natural size, one and three- tenths inches long and 

 four-fifths of an inch wide. Such are the dimensions of 

 the largest in our cabinet, but they are rarely found of 

 that size, we have them from the size of a grain of pepper 

 to the sizes mentioned above. They are often silicious, but 

 in some localities entirely changed into calcareous spar. 



Not much has been published respecting the geognostic 

 position of this fossil. Dr Goldfuss says that P. ovalis 

 occurs in transition limestone. In the United States they 

 characterise the upper strata of that (transition) forma- 

 tion ; they are of rare occurrence in the strata of lime- 



