GRAPTOLITES OF NEW YORK, PART 2 48 1 



preserved, which produce the mucronate appearance. The meshes extend 

 on either side of the rhabdosome to a distance equal to the width of the 

 rhabdosome. The nemacaulus is extremely thin, quite flexible and rarely 

 more than half the length of the rhabdosome. 



Position and localities. L . m u c r o n a t u s is in New York one of the 

 common graptolites of the Normanskill shale and found in all the principal 

 localities. Ami and Lapworth have recorded it from several outcrops of 

 the same horizon in the province of Quebec and Gurley has also found it in 

 beds belonging to his Upper Dicellograptus zone at Magog, Canada. The 

 same author cites it among the fossils of the Lower Dicellograptus zone of 

 Arkansas. In Great Britain, Carruthers, Nicholson and Lapworth have 

 frequently cited it and Lapworth's tables of 1880 showing the range of the 

 graptolites in Great Britain contain it as a Glenkiln species. The form 

 from the shales at Newham, near Lancefield, in Victoria, which has been 

 identified by Etheridge with our species is associated with species of the 

 Deepkill zones or Point Levis shales and represents a Retiograptus, closely 

 related to R. tentaculatus Hall. Neither can the Australian form, 

 identified by McCoy with this species, have been properly placed. 



Remarks. We have already shown that the mucros are always double, 

 and that their simple appearance in the compressed material is due to their 

 close union by the inclosed peridermal extension. 



Lasiograptus bimucronatus (Nicholson) 



Plate 29, figures 12-18 ; plate 30, figures 6-8 ; plate 31, figure 4 



Graptolithus sp. Hall. Pal. N. Y. 1859. 3:507, fig. 1-3 

 Graptolithus whitfieldi Hall. Can. Org. Rem. Dec. 2. 1865. pi. B, 



fig. 6-1 1 

 Diplograptus bimucronatus Nicholson. Ann. & Mag. Nat. Hist. 1869. 



4:236; pi. 11, fig. 12 

 Hallograptus bimucronatus Lapworth. Cat. West. Scott. Foss. 1876. 



p.7; pi. 2, fig. 58 

 Diplograptus (Hallograptus) bimucronatus Lapworth. Belfast 



Field Club. An. Rep't & Proc. Ser. 2. apx. 1877. pt 4, p. 134; pi. 6, 



fig- 23 



