266 NEW YORK STATE MUSEUM 



and thecae do not seem to bring out sufficient differences to warrant a 

 greater than varietal differentiation of the two, though the excavations may 

 be a little deeper and the introversion slightly greater than in L . f 1 a c c i - 

 d u s, but the principal difference lies in the form of the branches, whose 

 curvature is opposite to that of L. flaccidus, i. e. first concave and then 

 convex ; the branches are furthermore strongly ascending in their direction, 

 and therefore, in the majority of specimens, inclose a smaller angle (axil) 

 between their dorsal walls. The sicula and the aspect of the proximal 

 part of the rhabdosome are again suggestive of L. flaccidus with the 

 exception of the upward growth, assumed by the third and fourth thecae. 

 In these differential features, the form shows an approach to Dicellograptus. 



SYNDYOGRAPTUS gen. IIOV. 



Ety. ffuvduo in pairs, y[>n$u> I write. 



Rhabdosome consisting of two obliquely ascending main branches and 

 symmetrically disposed, ascending, parallel secondary branches, which are 

 given off in pairs. The thecae are of typical leptograptid character, with 

 straight ventral margins, slightly introverted apertural part and shallow 

 excavations. Also the structure of the sicular part of the rhabdosome 

 seems to be that of a Leptograptus. 



Genotype. Syndyograptus p e c t e n sp. now 



Although this genus in its general habit possesses considerable simi- 

 larity to Pterograptus Holm, it differs distinctly from the same in the paired 

 arrangement of the branches (in contrast to the serial arrangement of the 

 branches in the Swedish genus), even if Pterograptus were not a dicho- 

 graptid with pendant instead of ascending branches. The nearest lepto- 

 graptid genus to Syndyograptus, as far as the general arrangement of the 

 branches of the rhabdosome is concerned, is Amphigraptus Hall, which also 

 possesses paired secondary branches. Their development, however, is so 

 much concentrated at the center that a rhabdosome with radiating branches 

 results. It would be only necessary that in Amphigraptus each pair 

 diverge less widely and the rhabdosome would settle 011 its side as in 

 Syndyograptus, the result being an aspect of the rhabdosome very much 

 like that of the latter gfenus. 



