The British Species of Lutraria (lamelli- Branchia), with a Description of L. Angustior Philippi

The Lutrariidae are large lamellibranchs which burrow deeply in bottomdeposits on the shore and in shallow water. The foot is relatively weak, and they live permanently buried 30 em or so beneath the surface, maintaining connexion with the overlying water through their long siphons, which are united in a common sheath for practically their whole length. The commonest British species, Lutraria lutraria (L.) is found at low-water mark on shores of muddy sand, and offshore its siphons are sometimes taken by the dredge or grab. Another species, L. magna (da Costa) is more local, and appears to inhabit muddy deposits near the mouths of estuaries. It is a southern form, being occasionally found on the south and west coasts of the British Isles, and, like L. lutraria, its range extends southward to the Mediterranean. Examination of shells from offshore shell-gravel deposits near Plymouth has revealed the presence of a third form, which appears to correspond with the L. elliptica var. angustior of Philippi (1844), a variety subsequently noted by several other authors under different names. Although a distinct form, it has never been assigned specific rank, perhaps because many of the specimens found would have been dead shells washed up on the beach, in which the hinge-teeth, an important character for identification, are usually worn or broken. This form was taken by Ford (1923, 1925) at Plymouth, but was identified as L. magna, and I have also collected specimens from off other parts of the south coast of England (see Appendix for list of localities).