Cakdiid.e.- 



-MOLLUSCA.- 



-Dreissena. 



365 



shore to one hundred and forty fathoms. They are 

 gregarious in their habits, living ou sands and sandy 

 mud, in which they lie buried, often in prodigious num- 

 bers. Several are used as food, but none to the same 

 extent as the common coclile, Curdlum eJule, of our 

 own shores. This moUusk is in season from autumn 

 to spring, and great numbers are consumed in all our 

 coastward towns and villages. It is cue of the most 

 savoury of its class, and is said to be by many prefen-ed 

 even to the oyster. " It is equally good, raw and 

 cooked, dressed either by roasting or boiling, and gives 

 a delicious flavour to fisli sauce. Cockles also are often 

 pickled."^(For6es and Hanley.) " The Cockle-beds 

 at the mouth of the Tecs have long afforded employ- 

 ment to the poor of the neighbouring district. Besides 

 the home consumption, it is computed that £300 is 

 annually gained in Greatham by this occupation." — 

 (Stirtccs in Johnston.) la the Western islands and 

 Higlilands of Scotland this shell-fish frequently furnishes 

 a valuable article of food. Dr. Macculloch, in his 

 ■' History of the Highlands and Western Islands," says, 

 " Where the river meets the sea at Tongue, there is a 

 considerable ebb, and the long sand banks are produc- 

 tive of cockles in an abundance which is almost unex- 

 ampled." In 1824, a year of great scarcity, these banks 

 presented every day at low water a singular spectacle, 

 " being crowded with men, women, and children, who 

 were busily employed in digging for these shell-fish 

 as long as the tide permitted. It was not unusual 

 also to see thirty or forty horses from the surrounding 

 country, which had been brought down for the purpose 

 of carrying away loads of them to distances of many 

 miles. This was a well-known year of scarcity; and, 

 without this resource, I believe it is not too much to 

 say that many individuals must have died of want." 

 Lieutenant Thomas gives a similar account in the year 

 1852. In Sanda, among the Orkney Isles, during the 

 late failure of the potato crop, he says, many of the 

 poorer people subsisted almost entirely on cockles. — 

 {Forhcs and Hanley.) Immense quantities of the com- 

 mon cockle are daily brought to London, and sold, 

 along with periwinkles and whelks, in the shops and 

 streets. In Torbay the natives use as food the two 

 larger species of cockles, the Cardium aculeatum and 

 rusticum. These two species abound on the Paignton 

 sands in the neighbourhood of that sea-port ; and at 

 low spring tides they may be observed, showing their 

 fringed siphons just above the surfiice. The cottagers 

 know them by the name of red noses, and gather them 

 in large quantities. After cleansing them a few hours 

 in cold spring-water, they fry the fish in a batter made 

 uf crumbs of bread, and this allords a savoury and suf- 

 ficiently wholesome dish. — (Turton.) Where cockles 

 are very abmidant, the shells are used to burn into 

 lime. John Kay, as far back as 16G2, h.'s recorded 

 the fact of his seeing the pcojile on the Welsh coast 

 burning cockle-shells to make lime, which he moreover 

 asserted to be excellent. The genera are Cardium, 

 Bucardium, Cerastes, Aphrodita, and Cardlssa. The 

 species of this latter genus are known by the name 

 of the Ileart-cockle, and characterized by being of a 

 depressed heart shape with the valves prominently 

 keeled, the posterior slope flat, and the external surface 



often brilliantly coloured. The family is represented 

 in Plate 10, fig. C, by Cardium hians. 



Family— LEDID^. 



Tliough the shells of this family have been hitherto 

 placed along with Nucida in the fiunily ArcidiB, yet as 

 they have the mantle lobes freely open, but produced 

 posteriorly into two siplional tubes, they are now made 

 to lake their jjlace in the si\h-c\d.%s Sipkonopliora. The 

 shells of this family are cquivalve, oblong in shape, ajid 

 of a pearly lustre within. The hinge consists of a series 

 of small comb-like teeth on each side of the cartilage 

 pit; or as some describe them, the teeth are two in 

 number, elongate, nearly parallel with the hinge margin, 

 each divided into numerous transverse hook-like plates. 

 The genera into which the family is divided are Yuldia, 

 Leda, and Ctenoconcha. The family is represented in 

 Plate 10, fig. 7, by Yoldia lanceolata. 



Family— MODIOLARCID^E. 



This family, consisting of the single gemis htodio- 

 larca, have an equivalve, thin, fragile, ventrioose shell, 

 of an ovate or trapezoidal form, with prominent, con- 

 tiguous beaks, placed anteriorly. The hinge has two 

 small, oblique teeth in the right valve which receive 

 two corresponding ones of the left. There are only 

 two or three species known, and these are chiefly found 

 attached by a byssus to floating sea-weed in several 

 parts of the southern ocean, as at the Falkland and off 

 Kerguelen Islands. 



Family— DREISSENID.^. 



This I'amily consisting, like the last, of only one genus, 

 Dreissena, resembles closely in external appearance 

 the shell of the Mussels, Sfijtili, and has hitherto been 

 generally arranged along with them. The presence, 

 however, of two distinct siphons, one of which is very 

 small, and the other prolonged into a tube, necessitates 

 the separation of this genus from the Mytilidce. The 

 animals possess an elongate, slender, strap-shaped foot, 

 which secretes a byssus, and thus adapts tliem for 

 anchoring themselves, instead of leaping or crawling. 

 The shell is equivalve, very inequilateral, of a triangular 

 shape, and obtusely keeled. The beaks are terminal, 

 like those of the Mussels, and are furnished internally 

 with a transverse shelf or septum. The hinge is tooth- 

 less, and the cartilage external, marginal. Dr. Carpenter 

 has shown that the structure of the shell, as shown by 

 the microscope, is very ditl'erent from that of the Mytili, 

 the internal layer being com]iosed of large prismatic 

 cells. The species are inhabitants of fresh water, are 

 gregarious in their habits, ami attach themselves to other 

 shells, stones, and floating timber, by means of Iheir 

 byssus. 



DREISSENA POL YMORPHA. — The species upon which 

 the genus was founded has lately become naturalized 

 in this country, and the history of its introduction, as 

 given by Professor Forbes, is curious. Originally a 

 native of the rivers round the Black Sea, it has gradually 

 extended its range all over Europe. Capable of enduring 



