NO, 1596. DALMANELLAS OF THE CHEMUNG— Wit LTA MS. 43 
Orthis eifeliensis closely resembles Hall’s species Orthis Ieonenisis 
(Hall, 1867). It is common in the Eifelian Devonian. 
There are several other species from the European Devonian rocks 
belonging to this same group of Orthids, though less closely resem- 
bling species already described from New York than those cited above. 
The following may be mentioned: 
Orthis lunata Sowerby 1839.4 Ludlow and Old Red also cited by 
Verneuil.? 
Orthis canalicula Sechnur.° 
Orthis tetragona Verneuil.4 
REDEFINITION OF THE NEW YORK SPECIBS. 
In proposing to redefine the Devonian Dalmanellas of the New 
York upper Devonian, the great similarity of the Kuropean forms to 
ours is not overlooked. It is strongly probable that the European 
species are, genetically, very closely related to those of the New York 
Devonian. But for the purpose of discriminating geological horizons 
it 1s important to take notice of those characters by which closely re- 
lated forms express their adaptation to local conditions of environ- 
ment. In doing this it has been found necessary to break up some of 
our well-known specific groups, to give restricted definition to the 
types, and to apply new names to forms generally included with one 
of the restricted types but differing from it by the characters here em- 
phasized. To do the same for the European forms would require 
more exhaustive study of the European material than is practicable 
_at once, and when done it will not materially add to the value of our 
definitions of local forms for students dealing with them in practical 
study of our American formations, and it is believed that it can be 
better done after this analysis is accomplished. 
SUBDIVISION OF THE GENUS INTO SPECIES. 
The Dalmanellas of the upper Devonian of the New York geolog- 
ical province may be divided into the following groups, based upon 
characters which are associated with either the geographic distribu- 
tion or the geologic range of the species exhibiting them. 
To some of these groups specific names have already been applied. 
Those names have been adopted in their full sense in case the defini- 
tions do not confuse forms having different range or distribution. 
In case the characters selected for specific definition are so confused 
the author’s name is retained for that part of the species which in- 
cludes the forms first described by him as types of the species; and 
@ Sil Syst. Mureh., p. 611, pl. 111, fig. 12d and pl. v, fig. 15. 
® Geologie de la Russie, p. 189, pl. x11, figs. 6 a, b, c, d, Russia and Hifel. 
© Paleontographiea, III, 1853, p. 218. 
4d Geologie de la Russie, p. 214. 
