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. arcuata, M. princeps, M. bella, Hall, of the Lower Helderberg group ; M. lenta, 

 Hall, M. Doris, Hall, M. Wakotti, 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 Barranue 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 Whitfieluella. 

 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 CHAR ION ELLA, Billings. 1861. 



PLATE XLII. 



1843. Atrypa. Hall. Geology of N. Y. ; Rept. 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. Cfiarionella, Hall. Amei-ican Journal Science, vol. xxxv, second ser., p. 396. 



1863. Charionella, Hall. Sixteenth Rept. N. Y. State Cab. Nat. Hist., p. 40. 



1863. Charionella, Billing.s. Geology of Canada, p. 374, fig. 400. 



1867. Meristella, Hall. Palajontology 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. 



