556 NEW YORK STATE MUSEUM 



PLATE 31 



Genus lasiograptus Nicholson 



See plates 29, 30 



Lasiograptus mucronatus (Hall) 



See plate 29, figures 9-11 ; plate 30, figures 1-5 

 Page 479 



I, 3 Proximal portions of synrhabdosomes [see pi. 29, fig. 9, 10]. In 

 figure 1 the synrhabdosome has become entangled with the 

 nemacaulus of a Climacograptus. 



Normanskill shale, Glenmont, N. Y. 

 2 Enlargement of specimen to show the extrathecal structures 

 Normanskill shale, Mt Moreno near Hudson, N. Y. 



Lasiograptus bimucronatus Nicholson 



See plate 29, figures 12-18; plate 30, figures 6-8 

 Page 481 



4 Young rhabdosome, showing sicula and fibers 



Normanskill shale, Mt Moreno near Hudson, N. Y. 



5 Diagram of rhabdosome of Lasiograptus 



a Exterior aperture of extrathecal structure 

 b Aperture of theca 



Retiolites geinitzianus Barrande var. venosus (Hall) 



See plate 29, figures 7, 8 

 Page 469 



6 Specimen showing the straight axis, the lateral ledges, portions of the 



reticulate layer and of the continuous periderm 



7 Portion of rhabdosome showing the reticulate layer covering the axes 



on the lateral sides 



8 Specimen in which both axes have become compressed into one plane 



' Clinton shale, Genesee gorge, Rochester, N. Y. 



