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however, exists between these; in that encrinite evident marks are 
seen of its having been attached to a vertebral column ; whilst in this 
(the tortoise encrinite), there is no trace whatever of any mode m which 
such a combination could have been accomplished, 
Mr. Donovan s specimen is rendered particularly interesting by the 
two first bones of one of its arms being still adherent to one of the 
semicircular openings, and in such a manner as not only to show 
that its divisions were dichotomous, but also to furnish us with some 
slight intimation of the nature of the trochitulas of which this mem- 
ber was formed. The articulating surface of one of these may be 
seen to be evidently formed by a slight concavity, in the centre of 
which is a small foramen : two ridges, with a narrow intermediate de- 
pression, passing in a line from this foramen to the two opposite points 
in the circumference: this articulating surface closely resembles that 
of the fossil trochites depicted Plate XIII. Fig. 40. But even with 
this aid, I must acknowledge that my researches respecting the arms 
and tentacula of this animal have been entirely unsuccessful. 
Whilst striving to connect bodies together to form the ramifying 
arms of this animal, I however discovered two other species of en- 
crinites, possessing similar articulating surfaces with those of the ossi- 
culse of the arms of the tortoise encrinus, which I shall now proceed 
to place before you, with some other substances, which bear generic 
marks of distinction sufficient to warrant their being considered as be- 
longing to encrinites, although not always sufficient to admit of their 
being respectively connected, so as to make out their respective species. 
Following the particular character of the articulating surface of the 
trochitulie attached to the body of the tortoise encrinite, I first call 
your attention to a fossil body, frequently found in the Kentish chalk- 
pits, which IS of a cylindrical shape, and has at its ends two articu- 
lating surfaces, much resembling that which is observable on the ossi- 
cular attached to the tortoise encrinite. One of these bodies is repre- 
sented on its matrix, Plate XIII. Fig. 35, Its surface is smooth, and 
