GRAPTOLITES—GRAPTOLITOIDEA. 



27 



In shales of age of Beekmantown {Tetragraptus zone) of Canada 

 and New York. 



IV. Ptilograptus Hall. 

 Rhabdosome with branches 

 provided with two rows of alter- 

 nate branchlets. No traces of 

 thecal apertures have been found. 

 Ord.-Sil. 



7. Pt. plumosus Hall. (Fig. 



38.) Lower Ordovicic. 



Branchlets slender, filiform and 

 close set, diverging at about 40 , 

 and about 35 mm. long. 

 In shales of the age of Lower Chazy, in Canada and New York. 



Fig. 37. Dendrograptus flexuosus (Rue 

 demann, N. Y. State Mus. Mem.). 



Order II. GRAPTOLITOIDEA 



Lapworth. 



Suborder Axonolipa Freeh. 



V. Staurograptus Emmons. (Clonograp- 

 tus Hall.) 

 Rhabdosome cruciform at the center, ow- 

 ing to the rapid budding of the early hydro- 

 thecae. Repeated bifurcations produce a 

 large number of branches, hydrothecae long 

 and but slightly overlapping. Camb.-Ord. 

 8. S. dichotomus Emmons. (Fig. ig.){Clo- 



nogmptus proxi- 



Fig. 38. Ptylograptus 

 plumosus (Hall, Can. Org. 

 Rem.). 



Fig. 39. Staurograptus dicho- 

 tomus (after Matthew). 



matns Matthew). 

 Upper Cambric. 



Branches upward 

 of forty, the result 

 of repeated bifurcation. Thecae from 11 

 to 13 in 10 mm., in contact for a little 

 over a third of their length. Apertures 

 nearly vertical to axis. 



In the upper Cambric shales of eastern 

 Canada and United States {Dictyonema 

 shales). 



