TRENTON CONGLOMERATE OF RYSEDORPH HILL 27 



the specimens obtained agree in all essential features with the 

 New York form, as originally described by Hall, showing also 

 the extended cardinal line and the slight inflection of the 

 brachial valve toward the cardinal extremities (features which 

 are more distinctly shown in the figures given by Hall and Clarke^) 

 it bears from three to four marginal folds on either side and on 

 both valves, a character mentioned by Hall and Clarke and more 

 distinctly shown in the specimens described as Zygospira 

 a q u i 1 a bv Sardeson and asHallina nicolletibv Win- 

 chell and Schuchert. Hall reports the form from the " central 

 part of the Trenton limestone at Lowville and near Martinsburg, 

 Lewis county ". Of later collectors it is mentioned only by Dr 

 White from the Black river beds at Boonville and the Black river, 

 but not from the Trenton Falls or the West Canada creek sec- 

 tions. Hallina nicolleti is reported by Winchell and 

 Schuchert from beds corresponding to the Xew York Lowville 

 limestone and from the upper third of the Trenton limestone in 

 Minnesota and Iowa. More extensive observation in this state 

 may therefore show its range to extend from the Lowville lime- 

 stone through the Black river beds into the Trenton. (Groups 



6, 7) 



ZYGOSPIRA Hail 



Zygospira recurvirostris Hall 



Atrypa recurvirostris Hall. Pal. N. Y. 1847. 1 : 140 



Zygospira recurvirostris is not infrequently found 



in the pebbles of gray crystalline limestone in the Rysedorph 



hill conglomerate. The specimens obtained present no features 



distinguishing them from the typical material, with the possible 



exception that the sinus is rather weakly developed. Hall 



reports that this shell occurs in considerable numbers near the 



middle of the Trenton limestone near Martinsburg, Lewis co. 



and that it also has been seen at Lowville and Middleville. White 



found it in the Black river beds of the Rathbone brook section, 



as well as in various horizons of the Trenton Falls section. In 



Canada and in the west it rises from the Lowville beds into the 



Trenton. (Group 6) 



^ Pal. N. Y. 1892. V. 8, pt 1, pi. 54, fig. 47-48. 



