Ulphaceaster sarthacensis, nouveau genre et nouvelle espèce d'échinide Archiaciidae du Cénomanien (Sarthe, France)

A new genus and a new species of the echinoid family Archiaciidae from Cenomanian deposits in Sarthe (Paris Basin, France) are described. The genus Ulphaceaster nov. gen. can be distinguished from other archiaciids by its anterior ambulacrum, which is located in a deep groove running from the peristome to the apex where the test enlarges in a tea-spoon shape. The apical rostrum is taller and more slender than for species of the close genus Claviaster. The species Uphaceaster sarthacensis sp. nov. is known from the Saint-Ulphace locality only (Sables et Grès de Lamnay Formation, La Garenne quarry), where it is found in shallow marine sandy limestones, from infralittoral deposit environments.