Description of a new Graptolite. 189 
durable axial support. We know that this relative change does 
take place in the living genus of Antipathes, while in the Gor- 
gonize, the central axis and the cortical portion are both preserved, 
but only in virtue of the calcareous matter which enters into the 
constitution of the cortex. The axis being preserved in both 
these genera, while the cortical substance in one is subject to de- 
cay, renders it probable, I may say certain, that the central stem 
is in general the most indestructible portion of the zoophyte. 
_ We have been led to this course of reflection by the absence, 
in the Specimen which we are about to describe, of any central 
axis or stem, and the general tubular structure of the polyparium. 
In it, the cup-like denticles are inserted into a common con: 
necting tube, are unilateral and vaginated on their external sides, 
the side of one cup supporting the next one aboveit in the series, 
in which last feature it much resembles some of the living forms 
of Sertularide. oe 
From the appearance manifested in this specimen, we are in- 
clined to infer that Sertularide existed at the same time with Pen- 
natulide: in the ancient seas, and that on a more critical exami- 
nation of the subject,,some of the differences of opinion upon the 
origin of the Graptolites may be found more seeming than real. 
€ species of Graptolites which we have discovered differ 
materially from those figured by Murchison or Hall. We have 
not seen the monograph of Dr. Beck, but presume if he had des- 
cribed the species, it would have been frequently referred to, not 
less on accourit of its structure than the elegance of its form. 
We shall therefore describe it as a new species, giving it at the 
same time the name of Graptolithus Hallianus, after Professo 
Hall, whose labors in the field of American Paleontology so 
justly entitle him to this honor. 3 
Graptolithus Hallianus. 
Potyparrum hollow, well defined, branching in a graceful 
raceme, much branched, branches mostly on one side, never op- 
posite, with unilateral cells, each supporting the next one above 
it, no solid axis or stype. 
