40 CANADIAN FOSSILS. 
§ VI.—GENERAL CHARACTERS OF THE FAMILY OF GRAPTOLITIDH; WITH 
REFERENCE TO THE DISTINCTIVE FEATURES OF THE GENERA, AS KNOWN 
IN THE GEOLOGICAL FORMATIONS OF CANADA AND THE UNITED 
STATES. 
In the first section of this memoir, I have remarked upon the nature 
and general form of the graptolites proper, and the allied genera which I 
regard as belonging to the same family. The large accession to the 
number of species, and the great variety of new forms added to those 
formerly known, require an extension of the characters heretofore given. 
The numerous graptolites described by Nilsson, Hisinger, Bronn, 
Murchison, Hichwald, Portlock, Geinitz, Barrande, Suess, McCoy, Salter, 
Harkness, Nicol, Meneghini, myself, and others, were for the most part ina 
fragmentary condition, affording knowledge only of the simple stipe, the 
structure of its parts, and the arrangement of the cellules. From these 
fragments however we have derived the generic characters; while the modi- 
fications in form, and the order and relations of cellules, have furnished 
means of specific distinction in the greater proportion of those described. 
In maintaining the generic term Graptolithus for the forms which have 
the nearest relations with those to which the term was originally applied 
by Linnzus, M. Barrande has proposed two sub-genera, characterized 
by the presence of a single series, or of two parallel series of cellules, 
under the names of Monoprion and Diprion. The latter term haying 
been applied to a genus of insects, the name Diplograptus* of McCoy has 
generally been adopted. 
The distinction indicated would at one time have expressed a character 
perfectly trenchant ; but the discovery of such forms as G. ramosus ¢ and 
G. furcatus, shows the occurrence of both a single and a double series of 
cellules upon the same stipe, or, more properly, shows the basal portion 
consisting of a stipe, with two parallel ranges of cellules. The stipe, dividmg 
at some distance above its origin, is continued as two simple stipes, each 
with a single range of cellules. These cellules are on the outer margin, 
and are a continuation without interruption from those of the lower part 
of the stipe. Including these therefore in the same group with G. pristis, 
the subdivision indicated would have less value for the purposes of study ; 
but I believe these latter forms may be separated on other grounds, as will 
be shown farther on; so that with our present knowledge we may still 
* In the genera proposed by myself, I have chosen the termination grapius instead of 
grapsus, since the latter termination is in use in the nomenclature of crustacea. 
+ The subdivision of this species beyond the first bifurcation, represented in the Pale- 
ontology of New York, vol. i, pl. Ixxiii, fig. 3, is erroneous; the specimen consists 
of two individuals, the base of one being placed directly in the axil of the other. 
