188 Description of a new Graptolite. 
we compare the analogies in the organization of 
When the 
Gorgonide, the Virgulariz, and the Sertularie, “this difference of — 
opinion, in regard to the true place of the Graptolites, may, in some 
asure, be explained. The Gorgonide and Pennatulide have 
a long semi-calcareous or horny axis enveloped in a fleshy or cori- 
aceous covering ; the Polypi are inserted in, or rather constitute, 
this cortical envelope, which forms a common bond of association, 
and have no articulation with the central axis. In the Sertularia 
on the contrary, the corneous, or hard portion of the polyparium, 
is external—the axis is traversed by a fluid or gelatinous substance 
—the cup-like cells or denticles pertaining to the polypi are tubu- 
lar and have a connection with the material which occupies the 
interior 
In the relative changes which would materially take place after 
the death of these Polypi, it suggests itself to us that the more 
corneous or calcareous portion would be least liable to decay, and 
consequently more subject to fossilization, while oe Rare” 
or fleshy part would be subject to rapid decompositi 
It is well known that a destruction of the sonicle ‘cover as 
well as the horny or calcareous axis very frequently occurs, and the 
imperfect impressions which they leave, impart some uncertainty 
to the distinctions which have been founded upon them. More- 
over it is obvious that according to the position of the Polypi on 
the polyparium at the time of extinction, or the relative position of 
the sete to the surface of the rock, when subsequently brought 
to light, some variation in the appearance of the same species 
may give rise to unnecessary distinctions in an attempt at a re- 
gular classification of these bodies. 
r. Beck gives to Graptolites the following generic characters : 
a ates th elongatum, sublineare, acuminatum, 
obtusiusculum, statu fossili compressissimum serratum. 
“ Polypi alternantes cum tubulo communi centrali communi- 
cantes a fossili statu seepissime secati rarius bifarii oblongi acu- 
minati. 
It is sauce that the clause, “cum tubulo communi centrali 
-communicantes,” implies that the polyparium and the denticles 
are both tubular. The axis, in most of those which we have see 
- described, is represented as being capillary while it is not stated 
whether they are solid or tubular, or whether the sete or disse- 
-piments are tubular or clasping. With due deference to the 
opinion of Dr. Beck and others, I am inclined to believe that the 
species which I shall presently describe, and perhaps all others 
characterized by a hollow central tube and tubular cells for the 
reception of the Polypi, more probably owe their origin t0 
the tribe of Sertularia than to Virgularia—for we have seen 
- 
. .* Murchison’s Silurian System, p. 695. 
STi 
