On some Gasteropoda from the Silurian Rocks of Llangadock (Caermarthenshire)

Abstract

P rof . G room has sent me some pieces of rock of Silurian age, from Llangadock, containing a number of gasteropoda. These fossils occur almost entirely in the state of internal and external moulds. The former rarely show much structure, but by pressing wax into the latter the original form and ornamentation of the shells are frequently reproduced, in such a manner as to give a tolerably-good idea of the original. By this means I have been able to make out ten distinct forms, which are referable to seven different genera, but only seven are sufficiently well preserved to be specifically determined with any degree of certainty. They may be enumerated thus:— Plethospira [Ulrichospira] similis , sp. nov. Bembexia (?) Groomii , sp. nov. Bemhexia (?) sp. nov. Bembexia (?) Lloydii (Sow). Murchisonia [Goniostropha] Cambria , sp. nov. Murchisonia [Cyrtostropha] torquota (?) M'Coy. Loxonema sinuosum (?) Sow. Loxonema Grindrodii (?) Don. Gyronema Octavia (d'Orb.). Polytropina globosa (Schloth.) Two small external moulds from the Upper Ludlow Beds, of which the wax-impressions bear some resemblance to Cyrtostropha torquata (M'Coy) are too imperfect for certain identification. The same may be said of the much-worn internal mould from the Wenlock Beds, which possibly represents Loxonema sinuosum (Sow.). Besides these doubtful ones, there are three other species from Llangadock which have been previously described by other palæontologists, namely, Bembexia(?) Lloydii (Sow.), Gyronema Octavia (d'Org.), and Polytropina globosa (Schloth.). They all have a wide range, and cannot be considered characteristic of any particular horizon. Cyronema Octavia (d'Org.) is by