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The Diastoporidae are a group of adherent Polyzoa belonging to the suborder Cyclostomata. Busk defines the generic characters thus:—“Zoarium crustaceous or foliaceous, discoid or indefinite in outline; adnate and sessile, or pedunculate and erect; no cancelli ”*. This restricted definition limits the group to almost a single genus; for the Mesenteripora of Blainville is the only other genus classed by Smitt and Busk among Diastoporidae, and the non-cancellated surface separates this small family from the Discoporellidae. In this review of the recent and fossil Diastoporidae we must bear in mind the restriction formulated by Busk, because as we go backward in time the necessity of this caution will be apparent. The family was never prolific either generically or specifically; but in nearly all the seas, from the Lower-Silurian era to the present, representatives of the family are generally found in deep-sea deposits. Their geographical range now is chiefly northern; and their bathy-metrical range in the past was as variable as now. In his definition of the genus Diastopora , Busk says :† “Zoarium adnate, discoid or flabelliform, centric or excentric, margin entire or lobed; cells towards the centre wholly immersed, usually suberect, and partially free towards the margin; mouth elliptical or suborbicular, horizontal or oblique”† As there is no typical species in which the whole of these characters are preserved, we are compelled to seek them in the five species catalogued as recent and fossil by: Busk. But there are specific characters not embraced in the generic definition, to which I wish |
