GRAPTOLITES OF NEW YORK, PART 1 



559 



(6) The peculiar Deep kill form, Goniograptus perflexilis, 

 which is characterized by very long thecae, thin branches, very long branches 

 of the first order ("funicle") and large divergence of the branches of the 

 second order, bears an extremel}^ striking similarity in general appearance to 

 a somewhat more robust Dichograptus from the Skiddaw slates, viz D i c h o - 

 graptus separatus Elles. 



The following table gives a comparison of the characters pertaining to 

 their general appearance. 



Goniograptus 

 perflexilis 



Dichograptus 

 separatus 



Length of 

 branches of 

 fli-st order 



6 mm 

 6.35 mm 



Divergence of 



branches of second 



order 



90°-100° 

 105° 



Divergence of 



branches of third 



order 



70°-80° 

 70° 



Number of thecae 

 in 10 mm 



6-7 

 13 



Width of 

 branches 



A 

 .5 



If we, however, compare the characters of the thecae, we find that in 

 Dichograptus separatus they are more closely arranged, and more 

 inclined. As these differences are indicative of a condensation of the growth 

 of the branches, they may not be so prohibitive of a phyletic connection 

 between the two species as they would appear at first glance. 



Indeed, a perusal of the tables of measurements of the thecae of the 

 various supposed phyletic series distinctly brings out the fact, that in a 

 large percentage of the groups the thecal arrangement shows progressive 

 condensation in successive forms. To cite the more notable instances, the 

 inclination of the thecae increases in the group leading from B r y o g r a p t u s 

 r a m o s u s var. cumbrensis to Didymograptusindentus from 20" 

 to 30°, in that leading from the same species to D. furcillatus from 20° to 

 45° and in that leading again from the same species to D. bif idu s from 20° 

 to 45°, while the number of thecae at the same time increases from 9-10 to 

 13-14 within 10 mm. 



As the subequal length of the "funicles" of both species, Gonio- 

 graptus perflexilis and Dichograptus separatus, is proof of 



