GEOLOGICAL SOCIETY OF PENNSYLVANIA. 



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drical, has been subjected to forceable pressure; its pre- 

 sent greatest diameter is one-eighth of an inch ; from each 

 articulation spring 8, 10 or 12 leaves, which radiate 

 from the centre to the circumference, forming a pretty- 

 symmetrical star at each articulation, which diminishes 

 in size as we approach the superior extremity of the 

 stalkj the leaves varying from two- eighths to half an inch 

 in length, and being one-sixteenth of an inch in breadth, 

 the terminal star being reduced to a mere tuft. The 

 articular sheaths which exist in all the recent species 

 of this genus are barely visible in this fossil specimen ; 

 they may possibly have been destroyed by pressure; 

 remnants of the sheath are however visible, more parti- 

 cularly at the antepenultimate joint of the upper portion 

 of the principal stalk. 



Species of the genus Equisetum have been discovered 

 growing in all parts of the globe, with the exception of 

 New Holland ; yet very few fossil species have as yet 

 been found, and hitherto none in America. 



Mr Ad, Brongniart (vide Hist, des Veg. Foss., 2d liv- 

 raison) describes five species : one of these he states to 

 have been found in the tertiary, two species from se- 

 condary formations, and a third, of rather a doubtful cha- 

 racter, from the coal measures. 



Our species bears some distant specific resemblance to 

 the Equisetum Meriani, figured by Brongniart, pi. 12, 

 fig. 13, which was found in the iridescent marl of 

 Neuewelt, near Bale. 



Martin figures three fossils, (vide Petrifacta Derbensia, 

 pi. 20) all of different genera, under the name Phytoli- 

 thus plantites (stellatus). One of these, fig. 5, bears some 

 analogy to the present species, but is sufiiciently distinct. 

 A fine specimen of this Derbyshire fossil exists in the 

 Steinhauer collection of Mr Wetheril, now deposited 

 in the Acad. Nat. Sc. of Philadelphia. Fig. 4, of the 



