26o NEW YORK STATE MUSEUM 



p a n u 1 a t a. This approximation is, as figure 169 shows, due to a splitting 

 of the sicula and theca and subsequent flattening out of the parts, but in no 

 case does it assume the bell or cuplike shape of D . cam p a n u 1 a t a, as 

 figured by Nicholson and Lapworth. 



There is also a possibility that this form is an aberrant Corynoides, but 

 the extreme simplicity of its characters does not, for the present, warrant a 

 definite conclusion as to its taxonomic position. 



In the Normanskill shale of Schuylerville, Saratoga co., in a band of 

 very fine grained shale, numerous bodies occur which in shape and size 

 recall D. acuminata Nicholson. They are noted in the addendum. 



Family leptograptidae Lapworth 

 leptograptus Lapworth 



Hopkinson already recognized with great acumen the fact that G rap- 

 to 1 i t h u s flaccidus Hall could be referred to neither Didymograptus 

 nor Dicellograptus and Lapworth proposed the generic term Leptograptus 

 for the important group which it represents and which he found to be 

 characterized by the form of its thecae. It has the latter in common 

 with Pleurograptus and Amphigraptus, all of which were united in the 

 family Nemagraptidae. 1 Elles and Wood have elaborately described the 

 characters of the genus and clearly pointed out its relations to Didymo- 

 graptus and Dicellograptus. The facts which stand out as especially 

 important from the description, are the elongated sigmoid curvature of the 

 thecae, whose apertures are situated in depressions and are slightly intro- 

 verted, and the recognition of the presence of two crossing canals at the 

 base of the stipes. We have already discussed these characters and their 

 phylogenetic bearing in the introductory notes on phylogeny. 



The only representatives of Leptograptus in the faunas of Now York 

 are an earlier mutation of the genotype, two of its varieties; and L. 

 annectans. 



'Subsequently replaced by the more appropriate term Leptograptidae. 



