Genus Graptolithus. 163 



gile branches, and distant, obtase serrations. Two individuals 

 only have been obtained, but the form and habit are so precisely 

 alike, and so distinctive in both of these, as to mark it a very well 

 characterised species. 



Locality and Formation. — Island of Orleans ; Hudson River 

 Group. 



Collectors. — J. Richardson, and E. Billings. 



Graptolithus indentus. 



Description. — Fronds consisting of two simple branches, diverg- 

 ing at the base from a slender radicle, and continuing above in a 

 nearly parallel direction : branches narrow, slender ; serratures- 

 very oblique, somewhat obtuse, truncated above almost rectangu- 

 larly to the line of the rachis ; about twenty-four in the space of 

 an inch ; a depressed line reaching from the serrature to near the 

 base or outer margin of the branch where it terminates in a small 

 node ; surface of branches striate. 



This species resembles the 67. nitidus in form, except that it is 

 less divergent, the divergence from the base being at an angle of 

 about thirty-six degrees for half an inch or more, after which the 

 two branches continue nearly parallel. Though it is probable that 

 this character may vary in some degree, it seems nevertheless to 

 mark the species, and in numerous individuals of 67. nitidus I have 

 seen none with parallel or converging branches. The serratures 

 in the two species differ in some degree in form, and the propor- 

 tional distances, thirty-two and twenty-four, form a very charac- 

 teristic distinction. A single fragment of a branch measures six 

 inches, but the full extent when perfect is not known. 



Locality and Formation. — Point Levy ; Hudson River Group. 

 Collectors. — Sir W. E. Logan, and James Hall. 



Graptolithus nitidus. 



Description. — Frond composed of two simple branches, diver- 

 ging from a small radicle ; branches narrower towards the base,, 

 gradually expanding towards the extremities, which in perfect spe- 

 cimens appear to be rounded, and the last serrations a little short- 

 ened; serratures small, shorter at the base, and becoming gradually 

 developed as they recede from this point ; acute at the extremities, 

 almost vertical to the line of the rachis, and making an angle of 

 about sixty degrees, the two sides being almost equal in length - r 

 about thirty-two in the space of an inch. A well-defined groove 



