INTRODUCTION. 
The Crustacea discussed in this volume are, primarily, the species from the 
Devonian formations of the State of New York, and, incidentally, such species 
from other-horizons as it has seemed important to introduce into the work either 
for purposes of comparison or for the furtherance of our knowledge in other 
respects. Since comparatively few species of the North American Devonian 
Crustacea have been found to occur exclusively outside the limits of the State 
of New York, these extra-limital species, for the sake of completeness, have 
been brought within the scope of the work. The volume may, therefore, for 
the present be regarded as a monograph of these Devonian Crustacea (not 
including the Ostracoda). 
In the ensuing discussions of the species the order followed is taxonomic, 
although no single system of classification has been rigidly adhered to. The 
chronological arrangement of the species is therefore subordinated to the 
zoological order of the genera and families. 
I. Historical. 
The first published notice of the North American Devonian Trilobites was 
given by Alexandre Brongniart (“ Crustaces Fossiles,” 1822), who referred to 
his species Calymene macrophtalma, two American specimens, one of which is 
probably referable to the species Phacops bufo or P. rana, Green, and the other, 
a plaster cast of a specimen which subsequently served as the type of Calymene 
{Dalmanites] anchiops, Green. In 1824, Dr. James E. Dekay (Annals of the 
Lyceum of Natural History, New York), recognized the Calymene macrophthalma 
(= Phacops rana), “ on the Helderberg Mountain near Albany, and at Coshung 
Creek, near the Seneca Lake.” In 1832, Professor Amos Eaton (Geological 
Text-book), described the species Nuttainia sparsa (= Homalonotus Dekayi, 
Green), and Asaphus (= Dalmanites) selenurus. This work was followed, in the 
same year, by “A Monograph of the Trilobites of North America, with Colored 
