CardiidjE. MOLLUSCA. Dreissena. 305 
shore to one hundred and forty fathoms. They are 
often brilliantly coloured. The family is represented 
gregarious in their habits, living on sands and sandy 
in Plate 10, fig. 6, by Cardium hians. 
mud, in which they lie buried, often in prodigious num- 
bers. Several are used as food, but none to the same 
Family — LED1DH3. 
extent as the common cockle, Cardium edule, of our 
own shores. This mollusk is in season from autumn 
Though the shells of this family have been hitherto 
to spring, and great numbers are consumed in all our 
placed along with Nucula in the family Arcidoe, yet as 
coastward towns and villages. It is one of the most 
they have the mantle lobes freely open, but produced 
savoury of its class, and is said to be by many preferred 
posteriorly into two siphonal tubes, they are now made 
even to the oyster. “ It is equally good, raw and 
to take their place in the Siphonophora. The 
cooked, dressed either by roasting or boiling, and gives 
shells of this family are cquivalve, oblong in shape, and 
a delicious flavour to fish sauce. Cockles also are often 
of a pearly lustre within. The hinge consists of a series 
pickled.” — {Forbes and Hanley.) “ The Cockle-beds 
of small comb-like teeth on each side of the cartilage 
at the mouth of the Tees have long afforded employ- 
pit; or as some describe them, the teeth are two in 
ment to the poor of the neighbouring district. Besides 
number, elongate, nearly parallel with the hinge margin. 
the home consumption, it is computed that £300 is 
each divided into numerous transverse hook-like plates. 
annually gained in Greatham by this occupation.” — 
The genera into which the family is divided are Yoldia, 
{Surtees in Johnston.) In the Western islands and 
Leda, and Ctenoconcha. The family is represented in 
Highlands of Scotland this shell-fish frequently furnishes 
Plate 10, fig. 7, by Yoldia lanceolata. 
a valuable article of food. Dr. Macculloch, in his 
“ History of the Highlands and Western Islands,” says, 
Family — MODIOLARCIDH5. 
“ Where the river meets the sea at Tongue, there is a 
considerable ebb, and the long sand banks are produc- 
This family, consisting of the single genus Modio- 
tive of cockles in an abundance which is almost unex- 
larca, have an equivalve, thin, fragile, ventricose shell. 
ampled.” In 1824, a year of great scarcity, these banks 
of an ovate or trapezoidal form, with prominent, con- 
presented every day at low water a singular spectacle, 
tiguous beaks, placed anteriorly. The hinge -has two 
“ being crowded with men, women, and children, who 
small, oblique teeth in the right valve which receive 
were busily employed in digging for these shell-fish 
two corresponding ones of the left. There are only 
as long as the tide permitted. It was not unusual 
two or three species lino wn, and these are chiefly found 
also to see thirty or forty horses fi'om the surrounding 
attached by a byssus to floating sea- weed in several 
country, which had been brought down for the purpose 
parts of the southern ocean, as at the Falkland and off 
of carrying away loads of them to distances of man}’ 
Kerguelen Islands. 
miles. This was a well-known year of scarcity ; and. 
without this resource, I believe it is not too much to 
Family— DREISSENID.®. 
say that many individuals must have died of want.” 
1 
Lieutenant Thomas gives a similar account in the year 
This family consisting, like the last, of only one genus. 
1852. In Sanda, among the Orkney Isles, during the 
Dreissena, resembles closely in external appearance 
i 
late faibu’e of the potato crop, he says, many of the 
the shell of the Mussels, M ijtili, and has hitherto been 
poorer people subsisted almost entirely on cockles. — 
generally arranged along with them. The presence. 
{Forbes and Hanley.) Immense quantities of the com- 
however, of two distinct siphons, one of which is very 
mon cockle are daily brought to London, and sold. 
small, and the other prolonged into a tube, necessitates 
along with periwinkles and whelks, in the shops and 
the separation of this genus from the Mytilidoe. The 
streets. In Torbay the natives use as food the two 
animals possess an elongate, slender, strap-shaped foot. 
larger species of cockles, the Cardium aculeatum and 
which secretes a byssus, and thus adapts them for 
rusticum. These two species abound on the Paignton 
anchoring themselves, instead of leaping or crawling. 
sands in the neighbourhood of that sea-port ; and at 
The shell is equivalve, very inequilateral, of a triangular 
low spring tides they may be observed, showing their 
shape, and obtusely keeled. The beaks are terminal. 
fringed siphons just above the surface. The cottagers 
like those of the Mussels, and are furnished internally 
know them hy the name of red noses, and gather them 
with a transverse shelf or septum. The hinge is tooth- 
in large quantities. After cleansing them a few hours 
less, and the cartilage external, marginal. Dr. Carpenter 
in cold spring-water, they fry the fish in a batter made 
has shown that the structure of the shell, as shown by 
of crumbs of bread, and this affords a savoury and suf- 
the microscope, is very ditt'erent from that of the Mytili, 
ficiently wholesome dish. — {Turton.) Where cockles 
the internal layer being composed of large jirismatic 
are very abundant, the shells are used to burn into 
cells. The species are inhabitants of fresh water, are 
lime. John Ray, as far back as 1662, has recorded 
gregarious in their habits, and attach themselves to other 
the fact of his seeing the people on the Welsh coast 
shells, stones, and floating timber, by means of their 
burning cockle-shells to make lime, which he moreover 
byssus. 
asserted to be excellent. The genera are Cardium, 
DREISSENA POL YMORPHA.— The species upon which 
Bucardium, Cerastes, Aphrodita, and Cardissa. The 
the genus was founded has lately become naturalized 
species of this latter genus are known by the name 
in this country, and the history of its introduction, as 
of the Heart-cockle, and characterized by being of a 
given by Professor Forbes, is curious. Originally a 
depressed heart shape with the valves prominently 
native of the rivers round the Black Sea, it has gradually 
keeled, the posterior slope flat, and the external surface 
extended its range' all over Europe. Capable of enduring 
