366 NEW YORK STATE MUSEUM 



shale specimens from Watervliet and Troy are all uniformly narrow, and 

 compressed specimens would naturally be wider than the uncompressed 

 Trenton limestone material, as the shale specimens of I), amp lex i- 

 caul is from the Bakers falls indeed are. Hall's original drawings [v. 1] 

 seem to represent equally narrow and slender specimens, but they are taken 

 from the impressions left in the limestone by the broken-out rhabdosomes. 

 Partly pyritized specimens from Watervliet show distinctly the imbricating 

 thecae and the section characteristic of D . a m p 1 e x i c a u 1 i s , supporting 

 thereby the reference of this material to the latter species. But the uni- 

 formity of thinness in the rhabdosomes and the distribution throughout a 

 distinct horizon demand the recognition of our form as a type of varietal rank. 



Description. The rhabdosomes are long (37+ mm) and very slender 

 (usual width 1.2 mm, maximum width 1.4 mm) with concavo-convex section 

 (?) ; without any free nemacauli. Virgella and lateral spines, if present, 

 very inconspicuous. The thecal partitions distinctly shown on lateral sides, 

 sutural grooves lacking. Thecae numbering 13 to 14 in 10 mm (32—34 to 

 the inch), overlapping about one third their length, inclined 30 to 40 " ; 

 with straight to slightly sigmoidal outer margin (concave proximally, straight 

 to slightly convex distally) and straight aperture. 



Position and localities. In the shale at the power house at Lansing- 

 burg, at Watervliet and various outcrops at South Troy (Brothers quarry, 

 Ruscher's quarry, etc.), probably of Middle and Upper Trenton age. 



Remarks. The specimens from the power house at Lansingburg had 

 been originally [1901] identified by the writer with D . angustifolius; 

 though in some of the preservation states of the thecae suggesting that 

 species, they differ from it in widening much more gradually and growing 

 to greater length with relatively smaller width. 



Diplograptus (Glyptograptus) angustifolius (Hall) 



Plate 25, figures 19, 20 



Graptolithus angustifolius Hall. Pal. X. V. 1859. 3:515, figure 

 Graptolithus angustifolius Hall. N. Y. State Cab. Nat. Hist. 13th An. Rep't. 

 i860, p. 59, figure 



