6o NEW YORK STATE MUSEUM 



Strata are essentially vertical with slight undulations ; but at a distance of 

 about 250 feet from the south end of the cliff the strata become much 

 more irregular, maintaining their nearly vertical attitude but are folded 

 and slightly displaced among themselves and faulted against the more 

 erect strata of the main part of the mountain. The southern part of 

 the mass is composed of strata similar to those of the northern but 

 increasingly slaty in composition. In both parts of this Mt Joli massive 

 fossils were found, but they are by no means of common occurrence ; 

 moreover they are so wedged into the vertical strata that their extraction 

 is not easily accomplished. 



South flank. In the layers of the south flank of the mountain which 

 strike n. 30° w., are essentially vertical but with many undulations and 

 irregular inclinations toward the south, and are thin, fairly pure limestone 

 strata from two to five inches in thickness separated by sandy shale masses, 

 these species have been found : 



Hindia fibrosa (^Roemei-) ? 



Subretepora 



Dalmanella testudinaria {Dalmati) 



Rafinesquina sj). 



Strophomena sp. strongly geniculate form (very common) 



Parastrophia hemiplicata Ifall small form 



Zygospira cf. uphami Winchell &• Schuchert 



Ortonia sp. 



Ampyx hastatus Ruedeiiiaiin 



Tretaspis reticulatus Rtcedcmanii (very common) 



Calymmene callicephala Green 



Pterygometopus cf. intermedius {IValcoti) 



Ptychopyge ulrichi Clarke (common) 



Illaenus americanus Billings 



This very striking though small array of species is emphatically indic- 

 ative of early Siluric age, we may say in a general sense equivalent to the 

 Trenton, but can not escape the inference that it is early Trenton with 

 suggestions of Pretrenton age. The trilobites are specially noteworthy, for 

 Ampyx hastatus and Tretaspis reticulatus have been found 



