Observation on the Plates, 
The first requisite in plates illustrative of subjects in natural history is, 
undoubtedly, that they should represent with fidelity the object under inves- 
tigation, convey a correct idea of the whole, exhibit in a marked manner the 
generic and specific characters, and display the anatomical details in different 
points of view. The faithful execution and accomplishment of these objects, 
will generally plead an apology in the estimation of those whose object is 
scientific Knowledge, for the want of that peculiar delicacy and finish in exe- 
cution which is within the reach of the practised artist alone. 
In the plates representing the generic character of the Crinoidea, I have 
endeavoured by figuring separately the several parts of the cup-like portion of 
the animal, yet preserving them in their natural series, to convey an idea of the 
manner in which they are placed over and near each other in the living 
animal, the dotted lines directing the eye to their points of adhesion and 
insertion. In all these generic plates 1 have shaded, and in the Crinoidea 
inarticulata also coloured differently from the rest, those plates or joints essen- 
tial to the generic character, endeavouring by this means at once to direct the 
eye to these parts. This, I believe, is a mode of representation hot hitherto 
attempted in plates on natural history, the public will judge of its effect. I 
have applied it to other subjects of natural history, and found it very usefal 
where the character of the genus or species is well defined, where this is not 
the case, it has frequently led me to a further examination of the subject I have 
wished to represent, and thus furnished some interesting results. 
I have supplied from the combination of numerous specimens, a restored 
figure of some of the Crinoidea, such as I conceive them to have been when 
living, venturing, however, to indulge no further in this conjectural process, 
