SMART AND COOKE : MARINE SHELLS OF SCILLY. 293 



sandy gravel, also from the deep-water dredgings on similar 



ground. 

 P. costulata Turt. — With P. tellinella^ but much less com- 

 mon. 

 P. Ferroensis Chem. — St. Martin's Flats, fairly common, 



living at low water mark, spring tides. 

 P. vespertina Chem. — Sparingly found in all the sandy bays, 



living at low water mark, but never very abundant. 

 Amphidesma castanea Mont. — Any quantity of single 



valves from the Menavawr and Crow Sound dredgings ; 



the ligament being tender, perfect specimens are rare. 

 Mactra solida L.- — Not abundant, but fairly distributed in 



most of the sandy bays. 

 M. solida var. truncata L. — With the type; fairly com- 

 mon in Pentle Bay. 



Another well-marked variety occurs, intermediate 



between the type and var. trimcata. 

 M. solida var. elliptica L. — With var. truncata. 

 M. subtruncata DaCosta. — Same localities as the preceding, 



but not so common. 

 Lutraria elliptica Lam. — Common in sand everywhere at 



low water mark ; often very large. 

 Syndosmya prismatica Mont. — Crow Sound, in 8 fms., 



muddy sand ; also inside Round Island on a similar 



bottom. Common. 

 S. alba Wood. — With S. prismatica.^ equally common. 

 Scrobicularia piperata Bellon. — Seldom found except in 



one bay (Porth-hellick), on St. Mary's. 

 Solecurtus candid us Renier. — Not uncommon alive in 



clean sand, at low water mark, in the neighbourhood of 



Pentle Bay. 

 Solen pel lucid us Penn.— Numerous in 8 fms. muddy sand. 



Crow Sound and inside Round Island 

 S. siliqua L. — In sand at low water mark. 



