The genus _Dactylopora_ was founded by Lamarck[326] on some fossil specimens from the Calcaire Grossier and included among the Zoophytes. D’Orbigny afterwards included it among the Foraminifera, and the structure of the calcareous body has been described by Carpenter[327] and other writers on the Foraminifera. In a specimen of _Dactylopora cylindracea_ Lam. from the Paris basin, for which I am indebted to Munier-Chalmas, the tubular thallus measures 4 mm. in diameter; at the complete end it is closed and bluntly rounded. The wall of the tube is perforated by numerous canals, and contains oval cavities which were no doubt originally occupied by sporangia. The shape of the specimens is similar to that of _Diplopora_, but the canals and cavities present a characteristic and more complex appearance, when seen in a transverse section of the wall, than in the older genus _Diplopora_. Gümbel has given a detailed account of this Tertiary genus in his memoir on _Die sogenannten Nulliporen_[328]; he distinguishes between _Dactyloporella_ and _Gyroporella_ by the existence of cavities in the calcareous wall of the tube in the former genus, and by their absence in the latter. The oval cavities in a _Dactyloporella_ were originally occupied by sporangia; in _Diplopora_ and _Gyroporella_ the sporangia were probably borne externally and on an uncalcified portion of the thallus. • • • • • In addition to the few examples of fossil species described above there are numerous others of considerable interest, which illustrate the great wealth of form among the Tertiary and other representatives of the Verticillate Siphoneae. Reference has already been made to _Vermiporella_ as an example of a Silurian genus. Other genera have been described by Stolley from Silurian boulders in the North-German drift under the names _Palaeoporella_, _Dasyporella_ and _Rhabdoporella_[329]; the latter genus is compared with the Triassic _Diplopora_, and the two preceding with the recent _Bornetella_.