GRAPTOLITES. i 
graptolitic forms should be referred ; nor is it certain that the extensive 
series now presented can all properly be referred to a single family. 
General Portlock has suggested that these bodies may constitute ‘“ several 
genera belonging even to more than one order.”’* That they are true 
Polypi, I believe we shall be able to show, both from analogies already 
established by various authors, and also from their mode of development 
or reproduction as exhibited in some of the species. 
The specimens which have usually been observed or represented are 
simple disconnected stipes, doubtless the dismembered or fragmentary 
portions of fronds, which, presenting in the different species great varieties 
of form and aspect when entire, are nevertheless composed of parts so 
similar that these fragments, though indicating specific differences, offer 
little clue to a knowledge of the entire form. 
The name Graptolithus was established by Linnezeus in the first edition 
of his ** Systema Nature,” 1736, and applied by him to the straight or 
curved forms which are serrated (celluliferous) upon one side only, of 
which G. sagittarius has been regarded as the type.t The propriety of 
this term is more readily perceived in its application to the fragments of 
the stipes of monoprionidian forms than to the central portions of the 
body of the same. In the spirally-enrolled forms, or those with four or 
more stipes uniting in a central disc, as well as in the variously-branching 
forms, the analogy is not so perceptible. 
Taking those species which, in the form of their cellules and in the 
separated fragments of the frond, would be referred to Graptolites proper, 
and tracing them, as we are now able to do in many species, to their 
perfect condition, we find a great variety of form and mode of growth. 
In the simplest of these we have two stipes diverging from a radicle, or 
initial point; and the parts remain so complete as to admit of no doubt 
Fig. 1. 
ECO DDL» 
GRAPTOLITHUS PENNATULUS. 
that this is the entire skeleton of the animal. ‘The cellules near the base 
of the stipe are not so fully developed ; while also those near the extremi- 
ties have not reached their full dimensions, and the last one is sometimes 
barely perceptible, or just assuming its form from the common body. These 
characteristics are perceptible in the figures upon plates i, 11, and i. 
In the next stage we have four simple stipes diverging from an initial 
point, and all evidently entire, as shown in the development of the cellules. 
* Geological Report on Londonderry, &c., p. 318. 
} I shall elsewhere endeavor to show that G. scalaris is a diprionidian form exhibit- 
ing only one margin. 
