In the Tertiary formations, Spatangus, Scutella, Clypeaster, and other new genera appear, and many of the ancient ones are absent; or at least have not been observed. Of the genera printed above in italics, no living species are known. [Sidenote: ON COLLECTING FOSSIL ECHINODERMATA.] On collecting and developing fossil Echinodermata.--In the previous remarks on the fossil remains of radiated animals, we have pointed out those remains that are the most important and instructive, and should be sought for by the student. Thus, in collecting Crinoids, the receptacle or body should be the principal object of research, and if only detached plates can be extracted from the rock, their relative position should be carefully noted, and the specimens glued to a card or board, in their natural order; and some of the ossicula of the column, and of the arms, or tentacula, be placed with them. Mr. Miller dissected specimens of every genus, and has figured the separate plates or bones that enter into the composition of the receptacle,[302] and arms. Traces of the tentacula, and their subdivisions, must be sought for, and if discovered, should be removed with the stone to which they are attached, and the block be afterwards reduced in size by a mason's saw, and not by the blows of a hammer, which might displace the ossicula. [302] Natural History of the Crinoidea. If imbedded in Lias shale, or other fragile material, a thick slab should be removed, for greater safety in conveyance; this, when reduced to a convenient size and thinness, may be imbedded in a tray with plaster of Paris, or glued to a piece of thin, well-seasoned mahogany, or deal. The specimens of the _Pear Encrinite_ of Bradford, and of the Pentacrinites from Lyme Regis, in the British Museum,[303] were prepared in this manner. [303] Petrifactions, p. 78. The crinoideal remains in Chalk belong but to few genera; they merely require the usual manipulation of cretaceous fossils. The collector, however, should remember that the ossicula and plates of the receptacle (as for instance of the _Marsupites_), are but slightly adherent to each other, and the chalk must not be wholly removed, or these parts will become detached. The receptacles of the Apiocrinites of the chalk are rarely found with more than a few joints of the column attached; and I believe no vestiges of the arms have been observed: these parts are therefore desiderata, and should be diligently sought for: the radicles of these crinoideans are long, articulated, and branching, and without due caution may be mistaken for the arms, or for another species. The first remark will also apply to the Marsupite; any specimens with but a few ossicula of the arms are very precious. I may observe that there is yet much to learn as to the number of species and genera, and the peculiar characters of the Crinoidea of the chalk, and that any addition to our knowledge on this subject will be valuable.