Article: English Aptian Terebratulidae

Terebratulidae from the English Aptian are systematically revised and their external and internal characters investigated, the latter chiefly by means of serial sections and dissections. Some new terms are introduced, notably for the hinge plates, and others redefined. Five new genera are proposed: Rhombothyris (type sp. Terebratula extensa Meyer), Platythyris (type sp. P. comptonensis nov.), Sellithyris (type sp. Terebratula sella J. de C. Sowerby), Cyrtothyris (type sp. Terebratula depressa var. cyrta Walker), and Praelongithyris (type sp. P. praelongiforma nov.). These genera show some uniformity in the absence of reversed plication and of convex hinge plates, the types of hinge plate present being the horizontal, concave, and virgate. The cardinal process throughout is relatively small and the loop relatively short.Three main stratigraphical conclusions are drawn: (a) Aptian and Albian terebratulid faunas are clearly distinct; (b) Upper Aptian and Lower Aptian terebratulid faunas can be distinguished in England; (c) the Aptian fauna of England is very distinct from that of north-west Europe.