Description of the Nox-Marine Mollusca

Abstract

Nineteen species of mollusca were sent to us by Dr. Trechmann, which he had obtained by washing the clay. The species were:— Succinea putris (Linnaeus). Rare. S. pfeifferi Rossmässler? Do. Limnæa pereger (Müller). Common. L. palustris (Müller). Hare. L. truncatula (Müller). Do. L. stagnalis (Linnæus). Do. Planorbis lævis Alder. Common. P. crista (Linnæus). Do. P. umbilicatus (Müller). Rare. P. leucostoma Millet. Do. Valvata piscinalis (Müller). Common. V. cristata Müller. Rare. Unio sp. Do. Anodonta cygnæa (Linnæus). Do. Pisidium amnicum (Müller). Do. P. casertanum (Poli). Common. P. cf. lacustris B. B. Woodward. Do. P. nitidum Jenyns. Do. P. subtruncatum Malm. Do. P. hensloicanum (Sheppard). Do. Since there is an almost total absence of characteristic species, it is difficult to speak definitely as to the age of the bed. They are all living forms, but the abundance of Planorbis lævis shows that we are dealing with a deposit of some antiquity. If we judge from the known facts, the bed may well be the equivalent of the Cray ford Brickearths or rather later. Valvata piscinalis is not known to occur at an earlier horizon, and, although the examples