Dielasma and Its External Homeomorph Beecheria

Two externally homeomorphous genera have been found to be included in "Dielasma" of authors (non King 1859). Ambiguity was introduced into the generic concept early and eventually resulted in general acceptance of a generic diagnosis which excluded the genotype. Dielasma is here restricted to those species showing the essential characters of the genotype and is considered to be a senior synonym of Dielasmoides Weller, 1914. A neotype is designated for Terebratulites elongatus Schlotheim to replace the original type material destroyed in the war. The name Beecheria is revived for external homeomorphs of Dielasma having the internal characters of Beecheria davidsoni Hall & Clarke.