Maryland Geological Survey 101 



Eecently H. S. Williams has published an extended account of what 

 he calls the Tropidoleptus carinatus fauna of the Hamilton formation.' 

 Faunally he considers the Hamilton formation as including the deposits 

 between the top of the Onondaga limestone and the base of the Tully 

 limestone of central New York, which have generally been divided into 

 the Marcellus shale and the Hamilton beds. He writes as follows : 

 " Faunally, the series of sediments, as they are exhibited in central New 

 York (beginning at the top of the Onondaga (Corniferous) limestone and 

 terminating at the base of the Tully limestone), presents a continuity 

 which leaves no doubt as to the genetic succession of a common fauna 

 from the base to the top. In dealing with this fauna., only the species 

 between the limits of the top of the Onondaga limestone and the base 

 of the Tully limestone, when these are present, will be considered as 

 belonging typically to the Tropidoleptus fauna." ' It will be seen, there- 

 fore, that these sediments represent what Dana called the Hamilton 

 period, with the exception that they do not include the Tully limestone 

 which, where it occurs, Dana apparently regarded as forming the top of 

 this period;' that they correspond precisely with the Erian period or 

 group of Clarke and Schuchert,* and also according to the writers 

 opinion, with the Marcellus and Hamilton members of the Romney fonna- 

 tion of West Virginia and Maryland. Cleland in Ms " Study of the fauna 

 of the Hamilton formation of the Cayuga Lake section in central New 

 York "' has also limited the Hamilton formation as indicated above, stating 

 that "It is bounded above by the Tully and below by the Onondaga 

 (Corniferous) limestone." " . 



\\'illiams carefully tabulated the faunal lists of several students of 

 the Hamilton formation, as defined above, and from those of the writer 



'Amer. Jour. Sci., 4th Ser., Vol. XIII, 1902, pp. 421-432. U. S. Geol. Surv., 

 Bull. No. 210, 1903, pp. 42-68. 



^Ibid., p. 50. 



' Man. of Geol., 4th Ed., 1895, pp. 576, 593. 



* Science, N. S., Vol. X, Dec. 15, 1899, pp. 876, 877. Univ. of the State of 

 Nr?w York, Handbook 19, July, 1903, pp. 8, 22, 23. 



' U. S. Geol. Surv., Bull. No. 206, 1903, p. 20. 



