The Echinoid Directory

Twitchellia Lambert, 1916, p. 171

Diagnostic Features	Small, circular test with rounded ambitus. Oral surface slightly concave Apical disc central; gonopores small or not open Petals present, open distally and extending more or less to the margin Peristome central and circular Food grooves as shallow depressions towards peristome; unbranched Periproct opening on oral surface close to margin Plating details unknown Tubercles on oral surface small and scattered
Distribution	Pliocene of California, USA
Name gender	feminine
Type	Astrodaspis merriami Clark & Twitchell 1915 [=Orchoporus lamberti Grant & Hertlein, 1938], by original designation
Species Included	Lambert set up this genus with two species, T. merriami and T. packi. The former was placed in the species Orchoporus lamberti by Grant & Hertlien, 1938, p. 50, and the latter placed as a synonym of Echinarachnius merriami Anderson, 1905
Classification and/or Status	Clypeasteroida; Scutellina; Scutelliformes; Scutellidea; Scutellidaee. Monotypic; subjective junior synonym of Merriamaster (=Dendraster).
Remarks	Based on a small individual that may be a juvenile. It has been synonymized by Durham (1955) with Merriamaster Lambert, 1911. J. W. Durham 1955. Classification of clypeasteroid echinoids. University of California Publications in Geological Sciences 31(4), 73-198. Lambert, J. 1916 Revue critique de Paleozoologie 20, p. 171