GEOLOGICAL SOCIETY OF PENNSYLVANIA. 235 



holes, which in other Pentremites surround this aperture, 

 visible in our specimens, but although no traces of them 

 are to be seen in the present state of our fossil, they may- 

 have existed during life and have disappeared by their 

 fossilification, the summit in ray specimen being more 

 or less obliterated. 



There seems to be no doubt that these animals were 

 fixed by an articulated column, but in the perfect one 

 I possess, the base is only perforated in the centre, show- 

 ing the aperture of the alimentary canal, but no radiating 

 surface as is generally the case in that genus. 



The size of the largest I found, if entire, would be 

 about 1 inch in length. The only one that I have per- 

 fect is about half of an inch long, and one-fifth of an inch 

 in its greatest diameter. 



They occur in Ferry county, Tennessee, about two 

 miles west from Tennessee river, imbedded in an argil- 

 laceous limestone containing here and there green earth, 

 which renders this rock susceptible of disintegration. 

 This stratum lies below the coal measures, so that it must 

 be considered as belonging to the upper transition. 

 They are associated with trilobites, Calceola sandalina, 

 calamopora, terebratula, spirifer, producti, &c. 



An excursion performed during last spring was prin- 

 cipally undertaken to ascertain the geognostic position 

 of this interesting genus. We obtained some specimens 

 of it imbedded in limestone with an oolitic structure ; and 

 having in our several rambles in every direction over the 

 state never found the true oolite formation, as described 

 by Messrs Phillips and Conybeare, and which prevails 

 particularly in some parts of England, we became more 

 anxious to ascertain the nature of the strata in which they 

 occur, and we have now satisfied ourselves not only of 

 the geognostic position of the strata in which they are 

 inclosed, but also of the real construction of the remains 

 themselves. 



