128 
PALAEONTOLOGY OF NEW-YORK. 
without definite arrangement, or in concentric lines parallel to the 
margins of the plate, and often elongated in the same direction, some¬ 
times even forming continuous ridges. The pectinated spaces on the 
basal plate, and on 12 and 13, are elongate reniform, and those on the 
adjoining plates are triangular; neither being symmetrical or equi¬ 
lateral. From twenty to thirty bars may be counted in each of the 
pectinated spaces. 
Column composed of two distinct parts : the upper, consisting of about 
fifteen articulations, is flexible ; and the lower part, larger and of 
greater length, consists often of nearly twice as many joints, which 
are ancliylosed together, and usually covered on the exterior by a 
calcareous secretion of greater or less thickness. 
This fossil is better known in the rocks from the occurrence of numerous spindle- 
form bases of the columns, which taper gradually downwards, and contract abruptly 
at the upper end : these being solid, are preserved entire, while the upper parts of 
the column, with the body, have been destroyed. These columns are often silicified, 
sometimes entirely free from any marks of articulations, but, when well preserved, 
presenting a granulose surface; the granules often arranged along the line of the 
joints, but sometimes indiscriminately scattered over the surface. When these solid 
bodies are partially worn, the articulated character is distinctly shown; and they 
are seen to be composed of plates with deeply striated articulating surfaces, which 
are thus strongly interlocked. In the upper part of the column the outer margins 
of the joints overlap the next one below, and the jointed structure may sometimes 
be traced into the upper part of the solid portion. The lower part of the column is 
rarely preserved without thickening of the surface, as in fig. 7. 
The form of the body is like Apiocystites of the Niagara group, but more expanded 
in the upper part, and with a greater proportional dissimilarity between the anteal 
and posteal half of the body. It differs much from Callocystites , and indeed from 
all the other cystidians of the Lower Helderberg and Niagara group, none of which 
are known to possess the character of having the lower half of the column solid. 
In the arrangement of the arms there is no essential difference between this and 
Callocystites or Apiocystites , except that in this one the ossicula are somewhat more 
prominent above the plates of the body. 
The species has a wide distribution, having been found in fragments over many 
hundred miles in extent, and indeed almost wherever the formation is known; and 
the great numbers of these fragments indicate the abundance of the species in these 
ancient seas. 
