776 NEW YORK STATE MUSEUM 



PLATE 15 



Genus didymograptus McCoy 



See pi. 13, 14 



Didymograptus bifidus Hall (sp.) 



Page 689 



1 Typical specimen. x2 



2 Smaller rhabdosome 



3 One of the largest and most complete rhabdosomes observed. x2 



Graptolite bed 3 of the Deep kill section 



Didymograptus nanus Lapworth 



Page 692 



4 Mature rhabdosome 



5 Proximal part of a rhabdosome. x5^ 



Graptolite bed 3 of the Deep kill section 



Didymograptus caduceus Salter eonend. Ruedemann 



Page 693 



6, 7 Two specimens showing the prevailing expression of the form at the 

 Deep kill. Natural size 

 Graptolite bed 2 of the Deep kill section 



Didymograptus caduceus Salter nanus mut. nov. 



Page 698 



8, 9 Two typical rhabdosomes. x2 



Graptolite bed (> of the Deep kill section 



Didymograptus forcipiformis sp. nov. 



Page 699 



10 Typical rhabdosome 



1 1 Young rhabdosome 



12 Branch of a long and thin branched rhabdosome 



13 Specimen showing the large angle of divergence of the branches 



Ash hill quarry, Mt Moreno, Columbia co. N. Y. 



