362 NEW YORK STATE MUSEUM 



Diplograptus amplexicaulis Lapworth. Roy. Soc. Can. Proc. & Trans. 



1886. 4:184 

 Diplograptus amplexicaulis White. X.Y.Acad. Sci. Trans. 1895. 15:93 

 Diplograptus foliaceus mut. amplexicaule Gurley. Jour. Geol. 1896. 



4:298 

 Diplograptus (Glyptograptus) amplexicaulis Freeh. Lethaea Pal. 



1897. 1 : 632 

 Diplograptus amplexicaulis Ruedemann. N. Y. State. Mus. Bui. 39. 1901. 



p. 497 ff 



Description. Synrhabdosome not observed. Rhabdosomes of moder- 

 ate dimensions (maximum length 45 mm, maximum width 4 mm), rapidly 

 attaining the full width (in distance of 10 mm), which is then maintained ; 

 convex on obverse side, and concave on reverse side, both marked by the 

 interlocking thecal walls but without septal sutures. Sicular extremity fur- 

 nished with thin short virgella and two minute, straight lateral spines. 

 Sicula small (1.2 mm) and slender. Thecae tubular, with broadly subrec- 

 tangular section, not growing exactly in the axial plane of the rhabdosome, 

 but curving towards the reverse side (thereby causing the concavity of the 

 rhabdosome) with slightly curving thecal walls (outer margins slightly con- 

 vex), numbering 13 to 14 in 10 mm (32-34 to the inch), inclined 30-40 , 

 overlapping one third, apparently without apertural mucros. Nemacaulus 

 not observed. 



Position and localities. In middle and upper Trenton limestone at 

 Trenton falls, at Middleville, Herkimer co., N. Y. Very common in black 

 shale at Bakers falls (Sandy Hill), Washington co., N. Y., where it tills a 

 great thickness of rocks, in association with C o r y n o i de s gracilis, etc. 



Remarks. Hall's original description is : " Stipes slender, linear, elon- 

 gated, surrounded by small sheathing folioles or scales giving it a serrated 

 appearance; folioles small, acute." The original figures were taken, as the 

 type shows, from a specimen retaining mostly the impression only ami 

 therefore narrower than the actual specimens. 



In the 20th Museum Report | [867] the same author has furnished two 

 very accurate enlargements of fragments of rhabdosomes, showing distinctly 



