3 68 



NEW YORK STATE MUSEUM 



3" 



Position and localities. Common in some layers at the Normanskill 

 (Kenwood) and at Glenmont near Albany, at Mt Moreno near Hudson, 

 Stockport, Columbia co., Lansingburg, Rensselaer co. and other outcrops 

 of the Normanskill shale. It has further been recognized by 

 Lapworth in beds of Kicking Horse (Wapta) Pass (Rocky 

 mountains of Canada), which are considered as of some- 

 what older age than the Normanskill 

 shale ; and by the writer in collections of 

 probably like age from Silver Peak Quad- 

 rangle, Nevada. Gurley has found it in 

 shales of Normanskill age from Arkansas. 

 Ami has doubtfully referred forms from the 

 neighborhood of Ouebec to D . angusti- 

 f o 1 i u s and the present writer identified it 

 in shales from New Jersey. In Great 

 Britain, Lapworth has recorded it as one 

 of the forms of the Glenkiln shales. D . 

 a n g u s t i f o 1 i u s had hence a very wide 

 distribution and was common to both the 

 Atlantic and Pacific basins. 



I am not aware that it rises here above 



Fig.311-14 Dipl ograp t u s an gust i foil u s ,1 -nt 1 "11 1 1 



the Normanskill shale. 



(Hall). Fig. 311 Copies of Hall's original figures 

 Fig. 312 Sicnlar extremity of a rhabdosome x 7. 

 Fig. 313 Portion of a typical rhabdosome from 

 Glenmont. Fig. 314 Specimen from Lansingburg, 

 N. V. x 5 



Remarks. Hall says of this species: 

 " The form and proportions of these den- 

 ticles are different from those of any species of graptolite in the collections 

 from these shales, and often more resembling the minute denticulations on 

 the fronds of fossil ferns than those of the graptolites." 



This peculiar form of the thecae which is well reproduced in the 

 original drawings [see text fig. 311] and is very characteristic of the species, 

 is largely due to the deep excavation of the outer wall of the proximal part 

 of the thecae and the resulting entering of thin shale films between this 

 excavated part of the theca and the preceding theca, whereby the thecae 



