10 
This last quality may account for the enlargement of the alimentary canal in the 
columns of the Acrinocrinites, CyaTuocrinites, &c, as the animal increased 
in size. 
On the summit of the column are placed series of ossicula, which, from 
their position and uses may be termed the pelvis, scapula, costal, and inter- 
costal joints or plates, varying in their number, and partly wanting in some 
genera. These form (with the pectoral and capital plates) a kind of subglo- 
bular body, having the mouth in its centre, and containing the viscera and 
stomach of the animal, from which the nourishing fluids are admitted through 
a sphincter muscle to the alimentary canal in the column, and also carried to 
the arms and tentaculated fingers. 
These ossicula, when possessing a short and thick figure, and connected by 
regular articulating surfaces, as in Apiocrinites, or occasionally perhaps, an- 
chylosing together, as in Evcentacrinites, I have denominated joints; when 
they assume a thinner and flatter form, and adhere only by sutures, lined by the 
muscular integument, as in Acrinocrinites, I have termed them plates. 
The difference of these modes of structure have enabled me to form four 
divisions of the family of Crinoidea ; and as the number of plates or joints on 
which the scapula rests, as also the number of fingers and arrangement of 
finger bones varies, these, with the shape of the column, offer good characters 
to form genera and determine species, 
The food of the Crinoidea we may conjecture to have consisted in animals 
‘ess solid than themselves, probably infusoria, polypi, meduse, &c. This indeed 
is rendered more certain by their possessing in their numerous tentaculated 
fingers, such an admirable net-like apparatus for the detention of minute sub- 
stances, since it is a rule in nature to suit always in its organic formations 
the mechanism to the wants. The small mouth capable of elongating into a 
kind of proboscis, also aids in confirming this conjecture. 
I apprehend that the Crinoidea propagated by eggs only, their complicated 
organic construction (so widely differing from that of the SreLLER1D#) not per- 
mitting increase by separation of parts of the animal, or by buds, as is said to 
be the case in Polypi, whose young are said to push forth from the sides of the 
gelatinous contractile body. The inference drawn from this alleged fact, 
