MACTRA. 353 



The lengtli of an ordinary-sized example is about an 

 inch and three-quarters, and its breadth about an inch and 

 two-fifths. " Worn shells frequently become deeply fur- 

 rowed or zoned with grey or slate-colour and sometimes 

 yellow." (Mont.) 



" Animal yellowish white or pale orange, subtriangular, 

 thick, the mantles freely open in front and fringed at the 

 margins. Siphons short, united to their extremities, the 

 branchial orifice rather larger than the anal one, the former 

 surrounded by about sixteen cirrhi. the latter with about 

 twenty, shorter and more regular than those of the branchial 

 tube. Both tubes of a pale yellow, pale brown, pale red- 

 dish, or flake-white colour, varying in examples from dif- 

 ferent localities. Foot large, fleshy, pointed when extended 

 and not furrowed by a byssal groove. By means of its 

 powerful agency the animal can leap for some distance. 

 Branchiae and labial palps of a reddish brown colour ; the 

 latter long, narrow, pointed, and triangular." (Clark, MSS.) 

 We find the animals of young and true specimens of this 

 species to differ from that of Mactra subtruncata^ in having 

 the sides of the united si^^hons smooth, and only faint 

 traces of a scabrous keel on the back of the anal one. The 

 orifice of the latter is furnished with a tubular valve, which 

 can be projected beyond the cirrhi. 



The Mactra solida is a common frequenter of most of 

 our sandy coasts all round Britain and Ireland. It is 

 usually a littoral species, burying in sand or gravelly sand 

 near low water-mark. Thence it ranges, if the ground be 

 continuous and favourable, to a depth of fifteen fathoms, 

 (as in the west bay of Portland,) being most abundant 

 in about five or seven fathoms (as in the Frith of Forth). 

 In one instance it was dredged from water as deep as 

 thirty-five fathoms, at a distance of fifteen miles from 



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