78 The Lower Devonian Deposits of Maryland 



Lower Devonian in this region, which is best developed in the Helderberg 

 Mountains in the eastern part of the State. This area of the " Third 

 Geological District " was studied by Lardner Vanuxem/ who had at- 

 tended the School of Mines at Paris, France, he being the only American 

 then having had this advantage. The " New York System " embraced 

 all the Paleozoic strata of the State which are divided into 30 named 

 groups. The formations that are of particular interest in this connection 

 are those termed the 



Helderberg 

 division. 



Onondaga salt group [ = Salina of modern geologists], Water- 

 lime group [Rondout and Manlius], Pentamerus limestone 

 [Coeymans], Catskill shaly limestone [Kalkberg, New Scotland, 

 and Becraft], Oriskany sandstone, Caudagalli grit [Esopus], 

 Schoharie grit, Onondaga limestone, Corniferous limestone 

 [now included in Onondaga]. 



All these formations and the higher ones of the Erie division up to the 

 Catskill were included in Murchison's Silurian System, while the De- 

 vonian embraced the Catskill at the top of the New York System. The 

 New York State Geologists therefore did w-hat Barrande was doing in 

 Bohemia, that is, included all the Devonian of their respective localities 

 in the Murchisonian Silurian. The change came a few years later, after 

 de Verneuil's visit to America. 



In 1843 appeared Hall's Survey of the Fourth Geological District and 

 on page 18 is again seen the foregoing arrangement of fonnations into 

 the " Helderberg series." Here also it is stated that the Silurian System 

 " embraces the rocks and groups from the Utica slate to the Hamilton 

 group " and that the Devonian corresponds " to the Chemung and Portage 

 groups," and also includes " a portion of the Hamilton." 



In 1846, Ed. de Verneuil,' one of the ablest paleontologists of his time, 

 visited America to study the Paleozoic rocks. His preparation for making 

 correlations was far in advance of that of any other scientist, as he had 

 already studied the Paleozoic rocks of Eussia and Sweden and was familiar 



'Geol. N. Y., vol. iii, Surv. Third Geol. Dist., 1842, pp. 11-16. 



= Bull. Soc. geol. de France (ii), t. iv, 1847, pp. 646-710. This paper was 

 translated, condensed, and annotated by James Hall. Amer. Jour. Sci., vol. v, 

 1848, pp. 176-183, 359-370; vol. vi, 1849, pp. 45-50, 218-231. 



