THE DALMANELLAS OF THE CHEMUNG FORMATION, 
AND A CLOSELY RELATED NEW BRACHIOPOD GENUS 
THIEMELLA. 
By Henry 8. Witii1aMs, 
Of Cornell University, Ithaca, New York. 
The Dalmanellas have for many years been known to be well rep- 
resented in the Chemung formation of New York State. In the 
process of drawing a paleontological boundary across Watkins Glen. 
and Catatonk quadrangles at the base of the Chemung formation 
Dalmanella was discovered to be one of the most distinctive genera 
of the Chemung fauna.” Specimens of this genus are among the first 
brachiopods to show the coming of the new fauna in the sections of 
central New York. As the collections were elaborated, it was discovered 
that the representatives of the genus increased in size on ascending 
the Chemung; that certain characters distinguish the Dalmanellas 
of western New York from those of central New York, small and 
large; and that the published definitions of the species fail to note 
the distinguishing marks by which the evolution of species is in- 
dicated. These observations have led to the belief that a redefinition 
of the Dalmanellas of the Chemung formation will be helpful to 
students using fossils as a means of discriminating geological hori- 
ZOnSs. 
The Chemung Dalmanellas (particularly the small specimens) 
closely resemble Orthis testudinaria of the Ordovician. There are 
also several species in the upper Devonian of Great Britain and con- 
tinental Europe, which present much similarity to the New York 
forms. 
_ Without here attempting to show the exact place occupied by the 
Chemung species in either the geological evolution of the race or in 
its adjustment to world-wide conditions of environment, the present 
paper will attempt to define the characters which are definitely con- 
nected with range and distribution of the species for this limited 
portion of Devonian time and for the area of New York and neigh- 
boring States. 
In reporting species in previous papers on Devonian Paleontol- 
ogy the author has made no attempts to revise the definitions of 
@The Devonian Section of Ithaca, N. Y. Jour. Geol., XIV, 1906-7, p. 580 and 
MV, p. 104. 
PROCEEDINGS U. S. NATIONAL Museum, VOL. XXXIV—No. 1596. 
30 
