16 
PALEONTOLOGY OF NEW YORK. 
To Summarize the Characters ; 
These organisms, in their earliest recognizable conditions of existence, appear 
as a simple point or spec upon the surface of some other organism, becoming a 
slender enrolled tube where the volutions (so far as can be determined) may be 
in the same plane and having the form of Spirorbis, under which designation 
they have sometimes been described. In its farther development the body 
becomes an elongate, straight or sinuous tube. In the earlier stages these 
orgaisms, either singly or in groups, remain attached to the surface of some or¬ 
ganic or inorganic body, and the continuation of this parasitic condition depends 
upon the size of the body or extent of surface upon which they may continue to 
grow. Beyond the limits or extent of the surface affording means of attachment, 
they become free and continue their growth in a constantly expanding tubular form. 
In their earlier stages the substance of the fossil consists of an inner and an 
outer wall, which are in contact; the exterior becoming annulated at an early 
period, and the inter-annular spaces, or the upper inner margin of these annular 
growths, produce sharp interior annulations, which often extend considerably 
within the visceral cavity, so that when the exterior becomes worn away, or 
the fossil is cut through on one side of the center, they often give the aspect of 
a septate tube. 
In the first recognized stages of this organism, the tube is apparently smooth, 
but in the later conditions the annulations are conspicuous and again become 
gradually obsolete with the growth of the animal. The longitudinal striae, 
which are at first obscure, become developed with the growth of the tube, and 
continue a conspicuous feature after the obsolescence of the annulations. The 
intermural vesicular tissue becomes developed only with the expansion of the 
tubular growth, and especially after the organism has assumed a free condition 
of growth. 
In their earliest known condition these bodies are always parasitic, and they 
are not known to begin their existence as a free organism. Whenever, in their 
advanced state of growth, they occur in a free condition, it will be found that 
the initial point is wanting, having been broken off and the marks of the frac¬ 
ture still remaining, or the surface has become cicatrised. 
