766 NEW YORK STATE MUSEUM 



PLATE 10 



Genus tetragraptus Salter 



See pi. 9, 11, 12 



Tetragraptus fruticosus Hall (sp.) 



Page 649 

 See pi. 9 



1 Young rliabdosome in which the branches have not yet commenced to 

 recurve 

 2, 3 Specimens with narrow, early recurving branches (var. tubiformis) 



4 A well developed specimen with somewhat later beginning geniculation of 



the branches. Shows broad nema (nemacaulus) 



5 Younger rhabdosome with the characters of var. tubiformis 



6 A rhabdosome intermediate between the preceding and following forms. x2 



7 Form with very late geniculation of the branches (var. campanulatus) 



and broad nema 

 8-10 Specimens with extremely late or imperfect recurving of the 

 branches 

 Originals are all from graptolite bed 2 of the Deep kill section. 



