66 



as to have induced the late worthy proprietor of this 

 interesting spot, Mr. J. Sherman, to consider them 

 as analogous in structure to the basaltic columns of 

 Staffa and the Giant's Causeway; he therefore main- 

 tains the extravagant theory that these columns are 

 nothing more than gigantic favosites.* We visited 

 this famous locality of trilobites not long since, and 

 were almost as much delighted with the sublimity 

 and grandeur of the cataract, and the picturesque 

 and romantic character of the glen, as with the re- 

 liques of olden times, which are scattered here in 

 such profusion. 



The genus Isotelus, derived from /V<j$, equal, and 

 TgAo$, extremity, is thus characterized by Dr. Dekay. 



Body oval often contracted, not unfrequently ex- 

 tended. 



Head or buckler large and rounded, equalling the 

 tail in size, but with two oculiform tubercles. 



Jlbdomen with eight articulations. 



Frontal process beneath, with two semilunar termi- 

 nations. 



Post abdomen or tail, broad, expanded with indis- 

 tinct divisions, as large as the buckler. 



Longitudinal lobes very distinct. 



Other distinguishing marks by which this genus 

 may be known, have been given in our introduction. 



* See a Description of Trenton Falls, by John Sherman, p. 17. 



