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 b}' 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 subsecpiently 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 macrophlhalma 

 (= 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 



