Report of the State Geologist. 



353 



The Crustacea described 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 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 Ameri- 

 can 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. 



L HlSTOEIOAL. 



The first published notice of the North American Devonian 

 Trilobites was given by Alexandre Brongniart (" Crustaces Fos- 

 siles," 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. De Kay (Annals of the Lyceum of Natural History, New York), 

 recognized the Calymene macrophtlialma (= Phacops rana), "on 

 the Helderberg mountain, near Albany, and at Coshung Creek, 

 near 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 Models of the Species," 

 by Jacob Green, M. D., accompanied by a Supplement in 1835. 

 This Monograph included several of the best known and most 

 characteristic of the Devonian species, namely : 



Calymene platys. A. (=.D.) myrmecophorus. 



Dipleura (Homalonotus) Dekayi. Calymene (=D.) anchiops. 



Calymene (=Phacops) bufo. Calymene? O&ontocephala—D. sele- 

 C. bufo. var. rana=Phacops rana. nurus. 

 Asaphus {=Dalmanites) plearoptyx. 



45 



