GRAPTOLITES OF NEW YORK, PART 2 



197 



the branches is as shown by the many parallel thecal walls composed of 

 numerous thecal tubes as in Inocaulis and Acanthograptus. 



The diagnosis of the genotype is as long as the genus remains 

 monotypic, that of the genus. 



Genotype. C a c t o g r a p t u s crassus sp. nov. 



Cactograptus crassus sp. nov. 



Plate 8, figure 1 



Description. Rhabdosome bushy, consisting of numerous thick 

 branches, which are gently and irregularly bent and bifurcate at long 

 intervals. The basis of the rhabdosome is not known. The (fragmentary) 



99 ^^f roo 



Fig. 99-101 Cactograptus crassus sp. nov. Fig. 99 Enlargement (x 5) of portion of branch showing 

 the form of the spines. Fig. 100 shows the terminal part of a branch ; fig. 101 suggests the spiral arrange- 

 ment of the spines 



rhabdosome of the type specimen is 90 mm long and 25 mm wide. The 

 branches are 3.5 mm wide measured between the tips of the denticles, and 

 still 2 mm between the interthecal notches, and distinctly striated longitu- 

 dinally. The denticles are triangular, bracketlike in shape. They overlap 

 about one half their length, are apparently arranged in a long slender 

 double spiral, number, in the compressed specimen, 8 in 10 mm on either 

 side of the branch, are inclined with their outer margin 20 to the axis of 

 the branch, while their apertural margin which is gently concave, is nearly 



