98 NEW YORK STATE MUSEUM 



account of its great vertical range, will be left out of consid- 

 eration. Also, Modiolopsis cf. aviculoides and 

 Spyroceras cf . a n e 1 1 u s are of little taxonomic value, 

 being poorly represented and not positively identified. 



O r t h i s tricenaria, D a 1 m a n e 1 1 a testudina- 

 r i a , D. subaequata var. pervetus Conrad, P 1 e c t o r - 

 this p 1 i c a t e 1 1 a , Dinorthis p e c t i n e 1 1 a, Pro- 

 tozyga exigua, Zygospira recurvirostris, 

 Lophospira b i c i n c t a , C 1 a t h r o s p i r a s u b c o n - 

 i c a , Trochonema umbilicatum, Gerasaphes 

 u 1 r i c h a n a , Illaenus a m e r i c a n u s , Pterygome- 

 topus c a 1 1 i e e p h a 1 u s , Ceraurus p 1 e u r e x a n - 

 themus and Leperditia fabulites extend partly 

 in the eastern and partly in the western province, from, the Low- 

 ville limestone into or above the Trenton limestone, and serve, 

 in the determination of the age of the pebbles under considera- 

 tion, by a process of elimination, to prove that the fauna to which 

 they belong originated in the Trenton period, and may belong 

 either to the Lowville, Black river, or Trenton epochs. P a ras- 

 t r o p h i a h e m i p 1 i c a t a ranges from the Black river 

 into the Utica beds, C o n r a d e 1 1 a c o m p r e si s a fromi the 

 Black river into Trenton beds, I s o t e 1 u s m a x i m u s from 

 the Black river into the Richmond beds. 



Several members of the fauna of the gray limestone pebbles 

 are thus far known only from the oldest epochs of the Trenton 

 period; these are Lophospira perangulata Hall sp. 

 Hall comprised two different forms under this one specific term; 

 that found in the conglomerate agrees more with the Lowville 

 limestone type than with the Trenton limestone type. Thaleops 

 o v a t a occurs in the west only in bed's of Lowville limestone 

 age, and in Canada in beds in which the Lowville and Black river 

 stages have not been separated. 



Isochilina armata var. p y g m a e a is a. variety of 

 a species found by Walcott in the Black river and Lowville lime- 

 stones, Schmidtella c r a s s i in a r g i n a t a, var. v e n - 

 trilabiata, and Eurychilina subradiata var. 



