HUDSON-RIVER GROUP. 
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Fig. 1 c. Section of the same. 
Fig. 1 d. Section and figure of a similar fragment of a column enclosed in a coral. 
Fig. 1 e. Fragment and section of a column where the discs are excavated on their upper side, and 
have plain rounded edges with a pentapetalous impression on the extremities. 
Fig. 1 f Fragment of similar character, having the upper edges of the plates fimbriated. 
Fig. 1 g. Section of the same, enlarged. 
Fig. 1 h. A magnified portion of 1 f showing the fimbriated edges of the discs. 
Fig. 1 i. Separate plates or discs of a similar column, showing the variable character of the marginal 
crenulations, one specimen being marked by six prominent angles. 
Fig. 1 k. Two figures, showing the proportionate size of the larger and smaller discs in the columns, 
composed of plain alternating joints. 
Fig. 1 l. A fragment of slate, with impressions of various discs of columns. 
Fig. 1 m. Several of the same enlarged, showing their analogy with the preceding and following forms. 
Fig. 1 n. Fragment of a column, with the edges of the discs rounded and slightly nodulose; inter¬ 
mediate plates thin. 
Fig. 1 o. Edges of the discs rounded and subnodulose; intermediate ones thin, nodulose. 
Fig. 1 p. Edges of the discs rounded and smooth, the intermediate ones thin. 
Fig. 1 r. Edges of the discs fiat and broad, the intermediate ones thin. 
Fig. 1 s. A fragment of slate with moniliform columns; the intermediate plates often being scarcely 
distinct, while in others they are half as thick as the larger ones. 
Fig. 1 t. Large fragments of columns in the compact slaty rocks of the Hudson-river group, with the 
discs thick, the intermediate ones being scarcely visible. 
Fig. 1 a. A similar fragment of a column, with a section of the end, showing its identity with the 
preceding figures. 
These figures illustrate nearly all the varieties of form usually seen in the columns 
of this species. There are some others presenting deviations greater than those figured, of 
which I have some doubt as to their specific identity, and therefore do not give them in 
this place. I have also entertained some doubt as to the propriety of uniting the figures 
from 1 n, pi. 78, onwards with the preceding, since I have not been able to trace a positive 
connection between the remote forms, though fig. 1 e, which is clearly identical with the 
preceding figures of columns, presents the pentapetalous impression on the extremity of 
the discs. 
Position and locality. This one is the most common species of this family in the western 
extension of the formation, occurring at Cincinnati (0.), Maysville (Ky.), and Madison 
(Indiana). In numerous localities in New-York, fragments of the columns are abundant, 
but I have never been able to find the body. Fragments of columns, well preserved, are 
abundant in western localities. Those figured are from Cincinnati (Ohio), Maysville 
(Kentucky), Pulaski, Turin, Loraine, Boonville, and other places in New-York. 
(State Collection.) 
I am indebted to Mr. Joseph Clarke, to Mr. Anthony, and to Mr. Carly of Cincinnati, 
for beautiful specimens of this species. 
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