102 NEW YORK STATE MUSEUM 



Spirifer crisp us is commonly deficient in plications 

 approaching" in this respect and in the character of the sinus, 

 S. eriensis from the Manlius limestone. A t r y p a 

 nodostriata is robust, convex, with coarse rounded 

 plications and rather faint concentric striations, characters 

 intermediate between A. reticularis of the Clinton 

 and A. nodostriata of the Rochester shale. Besides 

 these species and some not yet identified, the following 

 occur. 



Cephalopoda 



26 Orthoceras annulatum 



27 O. medullare (?) rare 



28 O. sp. 



Pelecypoda 



29 Modiolopsis cf. subalatus? 



The origin of these lenses is still obscure. -Many of the fossils 

 found in them are characteristic of the Niagara group of the west, 

 but are rare or wanting in the Niagaran of New York. This is 

 specially the case with the trilobites (Illaenus ioxus) and 

 the cephalopoda. Dr E. N. S. Ringueberg many years ago studied 

 these limestone masses as exposed at Lockport and other more 

 eastern localities, and he termed them the " Niagara transition 

 group". 1 He found in this rock 32 Niagara species, 11 species 

 common to the Clinton and Niagara, two species found otherwise 

 only in the Clinton, and two species not found outside of this rock. 

 The origin and significance of these unique deposits are being care- 

 fully studied by the state paleontologist. 



Rochester shale 



The Rochester (Niagara) shale has a total thickness of about 68 

 feet in the gorge of the Niagara. It is here divisible into a lower 

 and an upper half. The lower portion is a highly fossiliferous shale 

 with numerous limestone bands, and terminates in a series of thin 

 calcareous beds with shaly partings in all about 4 feet thick, and 

 extremely rich in bryozoa. The upper 34 feet are quite barren and 

 have few limestone layers. 



'Am. nat. 1882. 6:711-15. 



