1789 



Tebble, Norman. 1966. 



British Bivalve Seashells. Trustees of the British Museum (Natural History), 

 London. Alden Press Osney Mead, Oxford, 212 p. 



Venus (Mercenaria) mercenaria Linnaeus Quahog 



Plate 12, Fig. a; Text-fig. 57 Hard shell-clam 



Shell solid, equivalve; inequilateral, beaks in the front half of the 

 shell; rarely more than 5" (12-7 cms.) in length; broadly oval in outline; 

 a dirty white, light varnish-brown, dull grey or grey-brown in colour 

 occasionally with red-brown zigzag markings near the margins.* Periostracum 

 grey-brown. Ligament a deeply inset, dark brown elliptical band, behind the 

 beaks reaching half-way to the posterior margin. Lunule well defined, 

 broad, heart-shaped. Escutcheon indistinct. Sculpture of concentric lines, 

 raised here and there into ridges, and fine radiating lines. In young 

 specimens the ridges are present all over the shell but in the adult they 

 persist, after wear and tear, only near the anterior and posterior margins. 

 Growth stages prominent. Both valves with three cardinal teeth; in addition 

 there is present in each valve a rough tooth-like area behind the beaks and 

 immediately below the ligament; this area has the appearance of a 

 supplementary posterior cardinal tooth which has been broken off. No 

 laterals. Inside of shell white, sometimes deep violet about the adductor 

 muscle scars. Pallial sinus not deep, triangular. Margin crenulate. 



Venus mercenaria lives in mud, with stones and shells, from between 

 tide-marks to depths of a few fathoms, being most abundant a short distance 

 above low water-mark. It is a native species of the coast of N. America 

 from Nova Scotia to Yucatan where it is harvested in some places as a wild 

 crop for sea food. The first living specimens in the United Kingdom were 

 found in the Humber in 1860, but previously, in 1859, a dead shell, 

 probably originating in a ship's ballast, was found in the Mersey. Since 

 that time it has been reported from the Menai Straits, and unsuccessful 

 attempts have been made to introduce it into the Dee (Cheshire) and Mersey 

 estuaries, whilst large colonies have become permanently established in the 

 Solent, Southampton Water and Portsmouth Harbour. These populations may 

 have been introduced via the kitchens of Atlantic liners. 



In recent years experimental colonies have been introduced into the 

 R. Yealm, Devon, Poole Harbour, Dorset, the Fivers Crouch, Roach and 

 Blackwater and at Walton, Essex. Some of these were removed on completion 

 of the experimental period but specimens may still be found. The species 

 has been successfully cultivated on a commercial scale in the Solent and 

 has lately been available on the menus of some London hotels. 



Venus .mercenaria was introduced into various places in France in an 

 attempt to breed it for commercial purposes but none of these was successful 

 until 1910 when a population deposited in the basin of the R. Seudre became 

 properly acclimatised. This was the basis for a now flourishing clam 

 fishery. It has also been reported at various times from Brittany, where 

 colonies still survive, in Zeeland, the Netherlands and in Ostend Harbour, 

 Belgium. - verbatim copy from p. 118-119 of the original - J.L.M. 



*Around the British Isles these zigzags occur only on populations 

 imported in late years from N. America. 



1790 



Templeton, w. L. f R. E. Nakatani, and E. E. Held. 1971 



Radiation effects. In Radioactivity in the Marine Environment. Natl. Acad. 

 Sci., Washington, D.C.: 223-239. 



Cites work of White and Angelovic (1965, 1966), abstracted elsewhere in this 

 bibliography, and reproduces a figure, showing that for the first 25 days 

 Crassostrea virginica is much more resistant to radiation than Mercenaria 

 mercenaria, but after 8 days LD 50 for hard clam was greater than for oyster. 

 Radiation tolerances must be expressed as time curves rather than the usual 

 LD 50/30- ~ J.L.M. 



494 



