768 NEW YOKK STATE MUSEUM 



PLATE 11 



Genus tetragraptus Salter 



.See pi. 9, 10, 12 



Tetragraptus quadribrachiatus Hall (sp.) 



Pagre64.5 



1 Young rhabdosome 



Graptolite bed 2 of the Deep kill section 



2 A young rhabdosome referred to this species 



Graptolite bed 7 of the Deep kill section 

 8 Mature rhabdosome in which one of the branches has become laterally 

 compressed, thus giving a lateral view of the thecae 

 Graptolite bed 2 of the Deep kill section 



4 Common appearance and mode of preservation of the rhabdosomes in the 



shale 

 Graptolite bed 2 of the Deep kiD section 



Tetragraptus amii EUes & Wood 



Page 647 



5 Typical mature rhabdosome 



6 A younger rhabdosome showing the angle of divergence between the two 



pairs of branches 



7 Young rhabdosome compressed laterally 



Graptolite bed 2 of the Deep kill section 



Tetragraptus serra Brongniart (sp.) 



Page 655 



8 Young rhabdosome. x2 



9 Average specimen 



10 Enlargement of fragment of branch. x2 

 Graptolite bed 2 of the Deep kill section 



