One of the earliest notices of _Calamites_ in the present century is by Steinhauer[585], who published a memoir in the Transactions of the American Philosophical Society in 1818 on _Fossil reliquia of unknown vegetables in the Carboniferous rocks_. He gives some good figures of Calamitean casts under the generic name of _Phytolithus_, one of those general terms often used by the older writers on fossils. Among English authors, Martin[586] may be mentioned as figuring casts of _Calamites_, which he describes as probably grass stems. By far the best of the earlier figures are those by Artis[587] in his _Antediluvian Phytology_. This writer does not discuss the botanical nature of the specimens beyond a brief reference to the views of earlier authors. Adolphe Brongniart[588], writing in 1822, expresses the opinion that the Calamites are related to the genus _Equisetum_, and refers to M. de Candolle as having first suggested this view. In a later work Brongniart[589] includes species of _Calamites_ as figured by Suckow, Schlotheim, Sternberg and Artis in the family _Equisetaceae_. Lindley and Hutton[590] give several figures of Calamites in their _Fossil flora_, but do not commit themselves to an Equisetaceous affinity. An important advance was made in 1835 by Cotta[591], a German writer, who gave a short account of the internal structure of some Calamite stems, which he referred to a new genus _Calamitea_. The British Museum collection includes some silicified fragments of the stems figured and described by Cotta in his _Dendrolithen_. Some of the specimens described by this author as examples of _Calamitea_ have since been recognised as members of another family. [Sidenote: PETZHOLDT AND UNGER.] In 1840 Unger[592] published a note on the structure and affinities of _Calamites_, and expressed his belief in the close relationship of the Palaeozoic plant and recent Horse-tails.