206 
PALAEONTOLOGY OF NEW-YOEK. 
upon a larger pentagonal plate. In this one there is usually the introduction of a third plate 
between the two, then of two interstitial plates in the next series, and again two other plates 
in the third series, before the separation is complete. Sometimes the separation takes place at 
the first introduction of interstitial plates; and sometimes, instead of a single plate introduced, 
one of the other plates is extended laterally, to give width to the arm below the separation. 
It will be observed, therefore, that the structure and mode of bifurcation of the arms and 
fingers are peculiar in this species, and sufficient to distinguish it from any known species of 
this period. The large elongated body is likewise quite characteristic, when destitute of the 
arms. 
The column of this species is round, long and slender ; consisting in its upper portion of 
joints of unequal thickness and diameter, those of the largest diameter being nodulose on the 
edges. 
Fig. 1 a. A specimen preserving the greater part of the body, with several arms attached, which 
are nearly entire : the angle of bifurcation, and curving of the branches beyond, is 
very characteristic. The fragment of a column below is composed of parts originally 
belonging to the specimen, though perhaps not occupying this position in relation to 
the body. 
Fig. 1 b , c. The bifurcation of two of the arms, showing a slight difference in the arrangement 
of the plates at these points. 
Fig 1 d, e. Fragment and section of the column. 
Fig. 1 f, g • Enlargements of the same, showing the slightly nodulose margins of the alternating 
joints, the crenulations towards the margin of the section, and the round canal. 
Fig. 1 h. Another fragment of a column, showing the nodulose joints more distant from each 
other. 
Fig. 1 i. Section of the same. 
Fig. 1 k, l. Enlargements of the two preceding figures. 
Fig. 1 h shows the canal to be much larger than in 1 e, and the striated surfaces 
extending to it; while in e, g , there is shown a smooth space between the margin 
of the canal and the commencement of the stria?. 
Fig. 1 m, n. A fragment from the same column, farther from the summit, where the joints are 
equal and smooth; the canal is large, and the striae extending from its margin to 
the eircumference ptoduce a crenulated suture. 
Fig. 2. The body of another specimen, probably of the same species. Several of the plates in 
the centre of the figure are in part restored, in accordance to what appears to have 
been their original form and size. The opposite side of the specimen is entirely 
destroyed, so that it can not be compared with fig. 1 a , to which it is closely allied 
if not identical. It is not improbable, however, that this one may be a distinct species ; 
more particularly since it occurs in the limestone, while the other occurs in the shale 
below. 
Position and locality. Fig. 1 was found in the central or lower part of the shale, and fig. 2 
in the limestone above the shale at Lockport. (Collection of Col. Jewett.) 
