78 
PALEONTOLOGY OF NEW YORK. 
that of Meristella varies in its greater size, shallower median groove and more 
expanded surface. 
The loop has been demonstrated in the following members of the genus; M. lavis, 
M. arcmtay M. princeps, M. bella, Hall, of the Lower Helderberg group ; M. lenta^ 
Hall, M. Doris, Hall, M. Walcotti, sp. nov., of the Oriskany sandstone; M. nasuta, 
Conrad, of the Upper Helderberg; M. Barrisi, Hall, and M. Haskinsi, Hall, of the 
Hamilton group. Besides these species the following may with security be re¬ 
garded as congeneric; M. Meeki, M. subquadrata, Hall, of the Lower Helderberg; 
M. lata, Hall, of the Oriskany sandstone; M. meta, M. rostrata. Hall, M. lens, 
Winchell, of the Hamilton group, and perhaps M. Houghtoni, Winchell, of the 
upper Devonian. 
From this list it appears that the genus was introduced, and attained its 
greatest development in species and numbers in the Lower Helderberg group, 
rapidly declining to its disappearance in the middle or upper Devonian. The 
genus has not been positively demonstrated in European faunas. In his earlier 
work on the Silurian Brachiopoda, Davidson referred several forms to this genus, 
and Barrande has used the name in connection with certain species from the 
Etages E and F; some of these English and Bohemian species may prove true 
Meristellas, while others evidently belong to Meristina and Whiteieldella. 
Tschernychew, also, has figured a form from the Goniatite-beds of the western 
slope of the Urals, as Meristella Barrisi, Hall ;* the fossil, however, is in many 
respects unlike the typical form of this species from the Marcellus limestone, 
and the accuracy of the generic reference of the Russian species is not apparent 
from an inspection of the figures. 
SuBGENus CHARIONELLA, Billings. 1861. 
PLATE XLir. 
1843. Atrypa, Hall. Geolog-y of N. Y.; Kept. Fourth Distiict, p. 171, fig'. 1. 
1860. Athyris?, Billings. Canadian Journal, vol. v, new ser., p. 278, figs. 35-38. 
1861. Charionella, Billings. Canadian Journal, vol. vi, new ser., pp. 148, 273, 274, figs. 100-102. 
1863. Charionella, Hall. American Journal Science, vol. xxxv, second ser., p. 396. 
1863. Charionella, Hall. Sixteenth Kept. N. Y. State Cab. Nat. Hist., p. 40. 
1863. Charionella, Billings. Geology of Canada, p. 374, fig. 400. 
1867. Meristella, Hall. Palaeontology of New York, vol. iv, p. 302, pi. xlvii, figs. 34-38. 
* Fauna des mittleren und oberen Devon am West-Abhange des Urals,[,1887, pi. xiii, figs. 1, 2. 
