770 NEW YORK STATE MUSEUM 



PLATE 12 



Genus tetragraptus Salter 



See pi. 9, 10, 11 



Tetragraptus woodi sp. nov. 



Page 662 



1 Young rhabdosome, which is so compressed that the angle of divergence of 

 the branches of the second order is shown 

 15, 16 Two mature specimens 



Graptolite bed 2 of the Deep kill section 



Tetragraptus similis Hall (sp.) 



Page 658 



2, 3 Two mature rhabdosomes laterally compressed and showing the common 

 mode of preservation 



4 A young rhabdosome spread out so that the branches of the first order are 



shown 

 Grraptolite bed 2 of the Deep kill section 



5 A mature rhabdosome compressed in such a way that two branches expose 



their lateral aspects in full width and two the frontal or dorsal 

 sides 

 Graptolite bed 1 of the Deep kill section 



6 A young rhabdosome showing well the proximal part and the rapid 



expansion of the branches. x2 



7 A mature rhabdosome showing an uncommon mode of preservation by 



which the branches have become unnaturally divergent 



8 Very early growth stage. Obverse side, showing the sicula and three 



thecae. x8 



9 A little more advanced stage showing a long nema. Obverse view. x8 

 10 Young rhabdosome showing nema and primary disk. Only the two 



branches of one side exposed. x6^ 

 Graptolite bed 2 of the Deep kill section 



