GRAPTOLITES OF NEW YORK, PART 2 



565 



similar characters and have frequently been identified with D. amp lexi- 

 cal! lis and which quite surely have descended from this form. 



Only few of these shale specimens, as that reproduced in plate 25, 

 figure 12, will exhibit the characteristic imbricating of the thecae along the 

 median line. 



a Diplograptus amplexicaulis var. pertenuis nov. 



Plate 25, figures 14-16 



Diplograptus amp lexi caule Whitfield. U. S. Geog. Sur. AVest 100th Merid. 



Wheeler's Rep't. v. 4, Pal. 1877. p. 19 

 Diplograptus amplexicaulis Ruedemann. N. Y. State Mus. Bui. 42. 1901. 



P-533S 



Professor Whitfield in 187s writes: 



Just south of Troy, in the shaly partings A 

 between layers of metamorphic limestone, I have X 

 found a species of Graptolite in great abundance \. 

 undistinguishable from G. amp lexi caule \ 

 Hall, from the Trenton limestone of Herkimer 

 county, N. Y. The same species was also found 

 abundantly in the yard of the arsenal at Water- 

 vliet by Capt. C. E. Dutton, U. S. A. 



The present writer has afterwards found the 

 same form in numerous localities in the region 

 indicated, by Whitfield, associated with other 

 Trenton forms. In most localities as at Water- w . 3 ° 8 "^309 3 10 



Fig. 308-10 Diplograptus am- 



vliet, it is the only graptolite observed and com- ^{ i ror^ofXur P e" 3 o8% n nd i 3 S I oTe 



- 1 r . 1 . , . 1 - . from Ruscher's quarry, Troy; that of 



pletely fills the rock there; at the power house in figure 309 is from Lansmgburg. * s 

 Lansingburg it is equally common in one layer and there associated with 

 a transitional fauna. 



After more thorough comparison of the Trenton limestone specimens 

 and those from the shales of the D. amplexicaulis zone, it has been found 

 that while the latter exactly agree in form and closeness of arrangement of 

 thecae with the Trenton limestone types of the species, they are distinctly 

 and uniformly narrower. It is true, there are limestone specimens, equally 

 narrow as that reproduced in figure 304, but they are extremes while the 



