Genus Graptolithus. 149 



greater. There is also some difference in the form of the branch- 

 lets. In separate branches the characters are too nearly alike to 

 offer the means of description, unless they are in a very perfect 

 state of preservation. 



From G. octobrachiatus it differs conspicuously in the form of 

 its branchlets, and in the comparative number and form of the 

 serratures. 



Locality and Formation. — Point Levy. 



Collector. — J. Richardson. 



Graptolithus quadribrachiatus. 



Description. — Frond composed of four simple undivided branch- 

 es, arranged bi-lateraly, or two from each extremity of the vincu- 

 lum ; branches slender, linear, obliquely striated, usually somewhat 

 incurved, serrated upon the inner side ; serratures a little recurved, 

 and mucronate at the tip; about twenty-four in an inch ; indented 

 to about one-third the width of the branch when completely flatten- 

 ed. Disk thick, strong, often extending along the branches and 

 giving them a somewhat alate appearance ; point of attachment of 

 radicle obscure. 



Almost all the specimens of this species are obscure, and all are 

 fragmentary ; in a few specimens only the serratures are exhibited 

 with some degree of perfection. The branches are preserved in 

 some specimens to an extent of two inches. 



Graptolithus cructfer. 



Description. — Frond composed of four simple strong branches 

 united by a small thickened disk ; branches broad, connected by 

 a short vinculum ; serratures nearly vertical to the direction of 

 the branch and sloping at an almost equal angle on each side, 

 acute at the extremity, and apparently mucronate or setiferous ; 

 about twenty-four in an inch. 



This species preserves the general character of G. quadribrachi- 

 atus, but the branches are much stronger, and about twice the 

 width. The serratures are scarcely oblique to the rachis, and are 

 very clearly mucronate at the tips, while some of them exhibit the 

 appearance of long setae. The imperfect preservation of the spe- 

 cimen examined renders it impossibfe to determine accurately the 

 nature of these appendages. 



In the specimen here described one of the branches is preserved 

 to the extent of two and a half inches, with a width of three-six- 

 teenths of an inch to the extremity of the points of the serratures? 



