NIAGARA GROUP. 
217 
resting partly upon the upper edges of the scapulars and partly upon the base of the arms, 
having on one side a- mouth composed of six small triangular plates forming a little conical 
elevation ; arms thirteen (the number sometimes variable), composed, from near the base up¬ 
wards, of a double series of slightly interlocking joints, which are sharply tuberculated on their 
surface and intermediately granular, a kind of foliaceous tentaculum attached to their inner 
margins ; tentacula with numerous oblique joints, which are narrow at their bases, and gradually 
expand on each side of a central line or midrib ; surface of the plates of the body marked by 
striae or rows of granules parallel to their edges, sometimes by tubercles irregularly arranged 
and more or less abundant; all the plates to the centre of the scapular plates marked by 
single or double rows of pores, which proceed from the base of the pelvic plates to the 
prominent upper angles, and from the basal angles of the costal plates to their centre, 
whence they radiate to each of the upper angles of the same plate, meeting corresponding 
rows from the centre of the scapular and interscapular plates. These pores communicate with 
the interior, and, though not always conspicuous, are present in some degree of development 
in every individual. The plates of the summit partake of the same variable character in their 
surface markings, as those of the body below. 
This very interesting crinoid combines within itself, in its numerous phases, the elements of 
many interesting developments, which become important characteristics in other forms of this 
class of animals. 
M. Yon Buch has given a very elaborate account of this species ; and it is quite evident 
that he has examined numerous specimens, to have seen all the phases which he describes : 
nevertheless there are some points in which our specimens present characters either not observed 
by him, or not described as we understand them*. 
It will be seen from the date of Say’s description, that this species has been a long time 
known, and for many years it was almost the only crinoid well ascertained in this country. 
The immense numbers which were found at Lockport, about the time Mr. Say described this 
species, placed it within the reach of every one, and they were to be seen in every collection!. 
*M. Von Buch gives the author credit for having given (Geol. Rep. 4th District) the best figures of this fossil 
yet published, though without a description; and yet he says that many parts have been misunderstood, or inac¬ 
curately represented! It will be perceived that the present description does not, in some particulars, correspond 
with that of M. Von Buch, though it does with numerous specimens in the author’s collection. By comparing 
the two, it will be observed that some points have escaped the attention of this very careful observer himself; and 
if the specimens figured in the Geological Report are compared with the figures there given, no great inaccuracies 
will be found in any parts represented. The smaller specimen there given is remarkable for the irregularity in the 
pores of the costal plates, and the occurrence of interrupted double rows from the centre obliquely to the basal 
angles. At the time when the figures of the interior of the costal plates were given (Tables of Organic Remains No. 
19, figs. 5, 0 and 7 at the end of volume cited), showing the distribution of these pores, and their connexion with the 
internal structure of the animal, as now described, the author supposed they could be understood without the aid of a 
description. 
t This period was at the time of the excavation for the Erie Canal, when these crinoids were found in immense 
numbers at Lockport, from which place Mr. Say’s specimens were obtained. Many hundreds, and probably thou¬ 
sands of individuals, were obtained at that time; and one gentleman informed me, that at one time, he had half a 
bushel of them. In all the specimens which I have seen, collected at that period, not one possesses the fragment of a 
[Paleontology — Vol. ii.] 28 
