When reading the very interesting article in the “Student” for October last, “On the Deep Sea,” by Dr. Carpenter, I was struck by the description of an Echinidan, which had been dredged up, and which is represented as looking “externally like a sea-egg flattened by pressure; it was about five inches in diameter, and of a brilliant crimson hue. Its test being composed of plates, separated by membrane, instead of being united by suture, was quite flexible, so as to resemble an armour of chain mail rather than the inflexible cuirass with which the ordinary Echinida are invested.” This statement as to the flexibility of the test so corresponds with what I have long suspected to be the case with some, at least, of the Crinoids, that I have been induced carefully to reexamine a large number of specimens, both of heads and columns of fossil, and to make some experiments on recent Crinoids; and I propose now to state shortly the result, and to suggest some points for the consideration of those who may take an interest in such subjects, and who are better qualified than I am, by their knowledge of the animal kingdom, to give an opinion on them.