GEOLOGY OF THE POUGHKEEPSIE QUADRANGLE 83 



limestone within the slates which will be described with this forma- 

 tion. 



Terranes present. Mather described the members of this 

 formation mider the headings, '' Hudson River Group," '' Utica 

 Slate " and '* Trenton Limestone Group. "^ He wrote of fossils 

 being found in the " slates and slaty altered limestones that would 

 not be recognized as limestones without close examination." The 

 locality was about one and one-half miles north of Barnegate- and 

 the fossils were recognized as belonging to the Trenton limestone. 



In 1878 T. Nelson Dale^ discovered fossils in the slates near 

 Vassar College and " on the Stormville road between Casper creek 

 and the first limestone ridge." Mr Henry Booth, of Poughkeepsie, 

 and students at the college found other fossils at the ledge near 

 the observatory at Vassar. The writer has also found fossils there. 



In company with Mr Booth, Mr Dale discovered other fossils on 

 the west of the Hudson opposite Poughkeepsie. This locality is on 

 the eastern slope of " Illinois mountain " southwest of Highland.* 



The fossils discovered by Dale were identified by Hall as : 

 Orthis (Dalmanella) testudinaria, Orthis pec- 

 tinella, Leptaena ( P 1 e c t amb o n i t e s ) sericea, 

 Strophomena alternata, Bythotrephis sub- 

 nodosa, Belle r op h on bilobatus and crinoid stems. 

 Specimens of the first five named are in the Vassar Institute Museum 

 at Poughkeepsie and are labeled " Highland, N. Y." O . ( D . ) 

 testudinaria and L.- (P.) sericea were found en both 

 sides of the river. Dale thought these fossils verified Mather's use 

 of the term "Hudson River Group." Certainly these strata belonged 

 to some member of the Trenton period. 



The first three types mentioned have also been reported from 

 Alarlboro-on-Ae-Hudson about nine miles north of Newburgh. They 

 have also been found in the slates at the northern end of the New 

 Hamburg tunnel." The writer has found fossils here, including 

 O. pectinella, in the shales under the bank, back of the 

 boathouse. 



1 Geology of the First District. Part IV, p. 369, 390, 397. 



2 loc. cit. p. 401. 



3 Amer. Jour. Sci. Ser. 3. 17:56-59. 



* Directions for reaching this locality were furnished b}^ Mr Henry Booth. 

 Take Modena road from Highland south one mile to cemetery, then wood 

 road through cemetery to mountain. Fossiliferous ledges occur 150-200 

 yards up the mountainside. 



5 J. M. Clarke. Guide to the Fossiliferous Rocks of New York Srate. 

 Handbook 15, p. 6. 



