TRENTON CONGLOMERATE OF RYSEDORPH HILL 31 



characteristic of this species, were found in the gray crystalline 



limestone pebbles and in a pebble of compact black limestone. 



In New York this species is also known from the Trenton beds; 



in Canada, the west, and the Cincinnati region, it has, however, 



been found to have its inception in the Stones river beds (Lowville 



limestone) and to pass through the Black river beds. (Croups 



5,7) 



Lophospira perangulata Hall sp. 



Murchisonia perangulata Hall. Pal. N. Y. 1847. 

 1:179 



In the gray crystalline limestone pebbles a number of internal 

 casts were found, which in the angularity of their volutions can 

 be compared only with Murchisonia perangulata 

 Hall, first described from the Lowville (Birdseye) limestone and 

 in a supposed variety also from the lower Trenton of Middleville. 

 Ulrich and Scofield hold the opinion that the two forms, united 

 by Hall under one specific designation, represent in reality two 

 different species, and refer a form from the western Stones river 

 group to the Lowville type of M. perangulata. While the 

 specimens from the Rysedorph hill conglomerate are a little 

 more slender than Hall's type specimen apparently was, they all 

 agree in the apical angle with some of the specimens figured 

 from the Stones river group, and it is thought that they come 

 nearer to the Lowville than to the Trentoii form. (Croup 7) 



LiospiRA Ulrich & Scofield 



Liospira americana Billings sp. 



PI. 2, fig. 7 



Pleurotomaria americana Billings. Can. nat. and 

 geol. 1860. 5:164 



Pleurotomaria lenticularis Emmons, Hall and 

 others (non Sowerby) 



In a pebble of black compact limestone collected at Rysedorph 



hill, a large gastropod, somewhat weathered on the surface was 



found, which in outline and profile fully agrees with the Trenton 



form described by Emmons and Hall as Pleurotomaria 



lenticularis, these authors regarding it identical with Sow- 



erby's Trochus jenticularis. Billings, recognizing the dif- 



