STUDY OF THE GRAPTOLITES. 203 



graptus), but imbedded in such a manner as to show a single series, which 

 would accord with the description of Linnaeus, while at the same time 

 the oblique direction of the cell margins (serratures) is more in accord- 

 ance with a Graptolite having a single series of cells ; but if the upper 

 line, limiting the linear figure, be a part of the fossil, it could not have 

 belonged to the latter group. The fact that it is wider than ordinary 

 forms of Monograftus would not, in my opinion, be a strong argument 

 against its beloning to that group; for at that period figures of fossils 

 were not always drawn in their true proportions. I have, however, been 

 inclined to believe the original to have been a Diplograptm, partly perhaps 

 from a name applied by Linn^us, and also from the fact that we meet 

 with numerous specimens in this group presenting scalariform figures, as 

 I have had occasion to show, while they occur more rarely and less dis- 

 tinctly among the others. It is scarcely probable that the figure of 

 LinNjEUS was intended to represent a fossil with rectangular cellules, like 

 Climacogi-aptus , notwithstanding the figure of Prionotus scalaris of Hisin- 

 GER is of that type ; nor does it seem to me at all certain that the latter 

 is identical with the species of Linnaeus.* This question, however, is of 

 minor consequence, since there is no longer an}^ important difference 

 of opinion among naturalists as to the general nature and character of 

 the fossil referred to in this description and figure of Graptolitlius. 



Until within a few years the Graptolites were, with two or three 

 exceptions, known only as simple, straight, or slightly curving linear 

 stipes or stems, usually lying in the same plane upon the slaty laminae 

 in which they were imbedded. Nearly all these were evidently fragmen- 

 tary, and though varying somewhat in their proportions, rarely exhibited 

 anything that could be regarded as the commencement or termination of 

 their growth or development. These bodies originally consisted of slen- 

 der tubes, composed of a corneous or chitinous substance, and having 

 more or less gibbosity ; but in their flattened condition, seldom preserve 

 more than a film of carbonaceous matter of extreme tenuity between 

 the layers of fissile slate in which they usually occur. The slender stipes 

 present a range of serratures either on one or both sides. Under more 

 favorable circumstances, these serratures are discovered to indicate the 

 apertures of cellules, symmetrically arranged in reference to each other, 

 and to the axis of the linear stipe. Others show parallel entire margins, 

 with transverse indentations across the central portion of the stipe. 



* I have elsewhere endeavored to show that G. scalaris is a diprionidian form, exhibiting only 

 one margin. 



