Brachiopods [from the Lower Carboniferous of the Menaian Region of Carnarvonshire

Abstract

The Producti belong, with a few exceptions, to the giganteus and the latissimus groups. The bulk of the material is poorly preserved and fragmentary. Some of the forms are new and undescribed, and one of these new forms, Productus aff. giganteus sp. nov. i, appears to be peculiar to the district. Productus giganteus (Martin) is represented by two big forms with a rounded outline (Ar 315, Ar 459) from D 2 , and a smaller specimen (Ar 381) from the D 1 limestone. Productus aff. giganteus sp. nov. i is a small form of the giganteus group, very globose and having a highly arched venter and large ears. The costæ are moderately coarse, and the shell has slight longitudinal folds developed below the spine-bases, which are numerous on the venter. This form is represented by a few well-preserved specimens from D 2 (Ar 314, Ar 254, Ar 257, Ar 374 e , & Ar 256 (=Brit. Mus. B 46780)). Productus aff. giganteus sp. nov. ii occurs in the D 1 limestone. Most of the specimens are in a poor condition (Ar 399, Ar 465, Ar 468, Ar 476, Ar. 478, & Ar 467 (=Brit. Mus. B 46781)). This form is coarsely costate, and approaches Productus maximus McCoy in size and ornamentation; but the ears are less strongly demarcated. There are examples of this form in the British Museum (Natural History) from the Upper Grey Limestone of Treflach, Oswestry, a higher horizon than that of Nantporth. The Treflach specimens are considerably more convex, but have similar ornamentation. Productus