Saxicava.- 



-MOLLUSCA.- 



-IIyad.e. 



3G9 



mantle is also aruply provided with muscular fibres, 

 running in all directions. The animal thus armed 

 attaches itself by the byssus to the rock it wishes to 

 perforate, then brings into contact with it this portion 

 of its mantle, and setting the muscular fibres into 

 motion, soon rasps away the surface. Wherever we 

 have a sea -coast of mountain limestone, the substance 

 of the rocks is almost invariably found riddled by 

 SaxicaviT. Sometimes they do considerable damage 

 to sea-walls. Some years ago, it was discovered that 

 the whole front of the Plymouth breakwater had been 

 attacked by them, and great alarm was e.\cited in con- 

 sequence for its safety. Luckily these little creatures 

 do not bore deeper than six inches, so that unless there 

 be a new surface exposed by the destruction of the 

 perforated part, there is not much danger to be appre- 

 hended from them. That this action does take place, 

 however, is unfortunately too well ascertained ; and no 

 doubt e.xists that the excavations made in limestone 

 rocks and indurated clay by the Saxicavse and other 

 lithophagoiis mollusca, contribute materially to alter 

 the configuration of the shores. " Their disintegrating 

 influence," says Dr. Johnston, " must have been at all 

 times, and must continue to be, considerable ; for it is 

 not merely by their own excavations that the opposing 

 rocks are reduced, but through them water is admitted 

 into their interior ; and aided by its macerations, its 

 varying expansions under various temperatures, the 

 ceaseless wearing away of this additional agent while 

 it flows or percolates through new channels opened to 

 ils access, the rock is speedily rubbed down into an 

 impalpable dust, or broken up into loose fragments. 

 Consider the result : the outline of the shore is altered, 

 a barrier to the tide removed, and perhaps some inroad 

 is made on the soil." 



Passing by the Pholadomyidce, we come to the 

 Razor- fish. 



Family- SOLENID^. 



The Solens or Razor-fish have an elongated shell, 

 equivalve, and gaping at both extremities. The liga- 

 ment is external, and the teeth are compressed, and 

 usually two or three in each valve. The animal has 

 a very large and powerful foot, which is club-shaped 

 or truncated in front, and not secreting a byssus. The 

 species are rather numerous, and are world-wide in 

 their distribution, and are usually found living buried 

 perpendicularly in the sand, into which they penetrate 

 their powerful foot, with its broad finger-like extremity, 

 enabling them to sink with great rapidity. They vary 

 considerably in shape, and in the structure of the hinge, 

 &c., so that it has become necessary to divide them 

 into several distinct genera. These are Soleri, Ensis, 

 Pharus, Cultellus, Siliqua, and Macha. The family 

 is represented in Plate 10, fig. 11, by Solen ensis. 



Aristotle was well acquainted with the Uazor-fish, 

 and has described one species very accurately under 

 the name of (r£dX»jv, most probably our common species, 

 S. vagina (:= marginatiis) . In more modern times it 

 attracted the notice of Reaumur ; but perhaps what 

 gave these animals their greatest celebrity, was their 

 excellent qualities as articles of food. They are said 

 Vol. II. 



to be about the best of shell-fish when properly cooked 

 (broiling being the best method), and are eaten in many 

 parts of Great Britain, as well as abroad. As has been 

 said, they generally bury in sand near low water mark, 

 and the valves of the shell, being connected by epider- 

 mis, serve at once as a protection and as a lining to 

 their holes. The existing species are distributed all 

 over the world without regard to climate. Several are 

 common on our own shores, and Professor Forbes has 

 given such a graphic account of one of them, the SoUn 

 vagina, that we extract it entire. It burrows in sand 

 near low-water mark at spring tides, to the depth of 

 from a foot and a half to two feet. " They lie in their 

 holes nearly vertical," he says, "and their places are 

 marked by perforations shaped like key-holes, corres- 

 ponding to the form of the extremities of their united 

 siphons. They are nearly vertical, and do not remain 

 quiet, but rise up and down now and then, shifting 

 themselves partly above the sand, as if to know what 

 is going on in the world above. When the tide goes 

 out, they sink deeper. The fishermen then endeavour 

 to tempt them out, as little boys would catch birds if 

 they could, by putting salt on their tails. The salt 

 penetrating the perforation, reaches and irritates the 

 extremities of the siphons, and the Solen, annoyed and 

 pained, rises suddenly to clear itself of the nuisance. 

 This vigilant human enemy watches the moment, and 

 seizes the opportunity, and the Solen — if he can catch 

 it ; but unless very quick in his motions, those of the 

 Solen may be quicker, and once aware of the danger 

 impending, the sensible shell-fish will not rise again, 

 but submits patiently to the indignity of being salted 

 alive, rather than run the risk of being caught anil 

 roasted, or else cut up for bait. But if it be not 

 touched, a second dose of salt will cause it again to 

 rise, which shows that knowledge and recollection of 

 the danger is the impediment to its reappearance in the 

 former case. Fishermen in England have a queer but 

 absurd fancy, that when the Razor-fish feels the salt, 

 it thinks the tide is coming in, and therefore rises in its 

 hole. If tlie Solen be taken out of its hole and placed 

 upon the sand, it immediately prepares to re-bury itself 

 It stretches out its foot to full length, and then bends it 

 so as to use the extremity as a kind of auger. Wlieii 

 the end has sunk into the sand, it draws up its shell, 

 which, first oblique, and afterwards perpendicular, soon 

 becomes immersed and rapidly disappears." 



Genus Glycimeris {-^Panopcra). — This genus 

 has a thick, equivalve, oblong shell, gaping at each 

 end, the beaks nearly central, and with one prominent 

 tooth in each valve. Some of the species are very large, 

 and are found buried deep in the sand at low water. 

 They are found principally in the Northern seas and the 

 Mediterranean; but extend also to the Cape of Good 

 Hope, Australia, New Zealand, and Patagonia. 



Family— MYAD^. 



The Gapers have a thick, strong, opaque shell, gaping 

 posteriorly. The valves are usually unequal and 

 covered with a wrinkled epidermis. The hinge is 

 without teeth, and the cartilage, which is internal, is 

 placed in a spoon-shaped cavity in one of the valves, 



3 A 



