GRAPTOLITES OF NEW YORK, PART 2 557 



Genus rktiograptus Hall 



Sue plate 29 



Retiograptus geinitzianus Hall 



See plate 29, figures 5, 6 

 Page 463 



g Specimen exhibiting- the ledges and continuous periderm. It is 

 obliquely split so that both rows of apertural meshes are seen, x 4. 

 Figure 1 1 represents opposite side of same fossil 

 Normanskill shale, Chatham, N. Y. 



10 Sicular end, showing sicula, form of thecae (on left side) and apertures. 



x 5 



Normanskill shale, Schodack landing, N. Y. 



1 1 Sicular end of rhabdosome, retaining the thick continuous periderm of 



the broad lateral face, x 4 



Normanskill shale, Chatham, N. Y. 



12 Portion of rhabdosome, showing the network of ledges with adhering 



wings of periderm. In the upper part four rows resulting from the 

 preservation of fragments of both sides are seen, x 5 



13 Compressed rhabdosome, showing the axes; the form of the apertural 



margins and the thinning out of the continuous periderm in anti- 

 sicular direction, x 4^ 



Normanskill shale, Schodack landing, N. Y. 



14 Sicular end of macerated specimen showing entire network of ledges. 



X4 



Normanskill shale, Kenwood near Albany, N. Y. 



15 Sicular specimen showing the sicula, x 4 



Normanskill shale, Schodack landing, N. Y. 



16 Reconstruction of network of ledges, after the specimens here figured. 



Cross ledges connecting the zigzag axes probably existed, but are 

 left out in the diagram as not positively seen. 



17 Reconstruction of exterior view of rhabdosome, showing the flat or 



slightly sloping lateral faces, the apertural margins and the apertures. 

 All originals are in the New York State Museum. 



