Genus Graptolithus. 1*71 



and sometimes twenty-six in an inch, usually obscure at the mar- 

 gins ; axis or mid-rib broad, often crenulate or serrate ; radicle 

 usually short ; frond robust. 



This species assumes considerable variety of form ; and from the 

 examination of a few specimens of the extremes of the series one 

 might be disposed to regard them as distinct species. After ex- 

 amining several hundred individuals however, I have not been 

 able to find reliable characters in the form, or subordinate parts, 

 to establish specific differences. The individuals figured represent 

 the principal varieties noticed, though a greater number of forms 

 might have been given. I have not thus far observed forms inter- 

 mediate between the short broad ones and the more elongate oval 

 ones ; but it is not probable that larger collections will furnish 

 such. The number of serratures in entire fronds varies in differ- 

 ent individuals from twenty-five or twenty-eight to fifty on each 

 side, depending on the size and form of the specimen. The small- 

 est examined have about twenty-five on each side. 



The specimens of this species examined are all so much com- 

 pressed that the rectangular arrangement of the parts of the frond, 

 as seen in P. ilicifolius, cannot be shown, the only evidence of 

 this character being the serratures along the central axis, which, 

 are transverse to those of the two sides. 



Locality and Formation. — Point Levy ; Hudson River Group 



Collector. — J. Richardson. 



Phtllograptus ilicifolius. 



Description. — Frond apparently broadly oval or ovate, with the 

 margin ornamented by mucronate points ; mid-rib or axis broad, 

 serrated ; the extension of the serratures broken off in the sepa- 

 rated laminae of shale ; radicle short. Serratures from thirty to 

 thirty -two in the space of an inch, varying slightly with the pro- 

 portionate length of the frond. 



The form in reality however is that of two broadly oval or ovate 

 leaves or fronds, joined rectangularly at their centres or by the 

 longitudinal axis, and in a transverse section presenting a regular 

 cruciform figure. The expansions of* the two sides, which are 

 laterally compressed, show distinct serratures or cells with pro- 

 jecting mucronate extensions. Those which are vertically com- 

 pressed have their outer portions broken off in the separated la- 

 minae of slate, and present the bases of the cells, which, having 



