IO 



NEW YORK STATE MUSEUM 



dently caused by a slight torsion of the branches, which probably is the 

 main differential character of the variety. 



Dicellograptus sextans var. perexilis no v. 



Plate 19, figure 2 



Cf. Dicellograptus sextans var. tenuibrachiatus Lapw. Roy. Soc. Can. 

 Trans. 1887. 4: 179 

 In a layer of the Normanskill shale at Mt Moreno D. sextans is 



represented by a variety, the most striking feature of which is the extreme 



thinness of its branches, the width of the latter amounting to no more than 



.2 mm. Besides, the angle of divergence of the branches is constantly 



smaller (270 in the proximal ] art 

 and 240 ultimately) and the 

 branches are more flexible. As a 

 result of these characters the habit 

 of the variety is entirely different 

 from that of the typical sextans, 

 but the form and arrangement of 

 the thecae and the presence of 

 mesial spines on all thecae place 

 it with that species. 

 From the narrow variety exilis this one is distinguished by its 



still smaller width (but half that of exilis) and the smaller angle of 



divergence. 



D. sextans var. p e re x i 1 i s is associated with Didymogr. sag- 



itticaulis, Nemagr. gracilis, and L a s i o g r . m u c r o natus. 



Dicellograptus moffatensis (Carruthers) var. alabamensis now 



Plate 20, figures i, 2 



Didymograptus moffatensis Carruthers. Roy. Soc. Edinburgh Proc. v. i, pt 2. 



1858. p. 469, fig- 3 

 Dicellograptus moffatensis Elles & Wood. Monogr. Brit. Grapt. pt 4 (Pal. 

 Soc. 1904) p.157 ; pi. 23, fig. ia-f 



Description. Branches of rhabdosome, as a rule, markedly straight, 



Fig. 233 Dicellograptus sextans 

 nov. Typical specimen, x 5 



: e x i 1 i s 



