Handbook of Paleontology 241 



beds and the overlying magnesian limestones occur- 

 ring between the Potsdam sandstone and the Pamelia 

 limestone. The limestones have been correlated with 

 the Tribes Hill limestone (Lower Canadian), but the 

 name has been retained for the passage beds between 

 the Potsdam sandstone and Hoyt limestone or Little 

 Falls dolomite which are missing in the type section. 

 The succeeding dolomites of the Canadian period also 

 are missing in this section so that the Tribes Hill is in 

 contact with the Pamelia limestone. The passage beds 

 have a characteristic lithology of their own. They 

 consist of alternating beds of hard vitreous sandstone ; 

 gray calcareous sandstone; blue or gray crystalline 

 dolomites and magnesian limestones ; black, oolitic 

 beds in some sections, blackish, crystalline, sandy lime- 

 stone in others. These beds have a maximum thick- 

 ness of 80 feet and contain trilobites and Lingulepis 

 acuminata. They occur everywhere in New York be^ 

 tween the Potsdam sandstone and Little Falls dolomite. 

 The Hoyt limestone is a more calcareous and more 

 fossiliferous phase of the lower portion of the Little 

 Falls dolomite, and is regarded as merely a local mem- 

 ber. The name was proposed (Ulrich and Cushing 

 '10), in place of the name "Greenfield" which was pre- 

 occupied, from the Lloyt quarry section near Saratoga. 

 The formation is mainly a dark gray or blackish, finely 

 crystalline or subcrystalline limestone with alternating 

 beds of blue and light gray dolomite. Beds of calcareous 

 sandstone and more rarely quartzose sandstone occur. 

 Eeds of black oolite occur most abundantly near the base. 

 Reefs of the calcareous alga, Cryptozoon, characterize 

 this formation, also the trilobites Tellerina hartii, Saukia 



