Cakditid^.- 



-MOLLUSCA.- 



-Anodosta. 



371 



ton Channel and Beliring's Straits to the Egean Sea, 

 and in depth from thirty to one hundred and twelve 

 fathoms. 



Family— CARDITID^. 



The species of this family have an ovate or cordate 

 shell, with the surface marked externally with strong 

 radiating ribs. The hinge is furnished with two oblique 

 diverging cardinal teeth directed towards the same side, 

 and no laterals ; the ligament is external. The species, 

 which muster upwards of fifty in number, are usually 

 obtained from deep water, on rocky bottoms in trojiical 

 seas, though some are found also in shallow water and 

 on the shores of North America. 



In tlie genus Cardita the shell is oblong ; while in 

 Venericardia it is cordate and ventricose. 



Family— CRASSATELLID^. 



In this family the shell is solid, ventricose, attenuated 

 posteriorly, smooth or concentrically furrowed, and of 

 a porcellaneous texture. The hinge is furnished with 

 two subdiverging, striated, cardinal teeth placed in 

 front of a cartilage pit, and one lateral tooth in each 

 valve. The ligament is internal, inserted in a pit in 

 each valve. The species, which are about thirty in 

 number, are usually dredged from deep water, and are 

 chiefly found in the Australian seas, thougli some have 

 also been obtained from India, Africa, and South 

 America. None have as yet been discovered inhabit- 

 ing Europe. 



Family— UNIONID^. 



The River Mussels secrete a byssus in the very young 

 state. The shell is usually regular, equivalve, and 

 closed. Externally it is covered with a hard, smooth, 

 olivaceous epidermis, beneath which it is beautifully 

 pearly. The ligament is external, large and promi- 

 nent, and the hinge is variable. The River or Pond 

 Mussels are found in fresh-water lakes, rivers, and 

 ponds throughout the whole world. About three 

 hundred species have been described — the greater num- 

 ber being natives of North America. In Asia and 

 South America a considerable number occur; and 

 though only a few species inhabit Europe, the number 

 of individuals belonging to them is very great. In the 

 Uiiionidce the sexes are distinct, and the eggs in tlie 

 females are contained in the outer gills, which in 

 winter and early spring are found to be full of them. 

 " The fry spins a delicate, ravelled byssiis, and flaps 

 its triangular valves with the posterior shell-muscle, 

 which is largely developed, wliilst the other is j'et in- 

 conspicuous." — {Woodward.) At this season. Lister 

 says that the Unio pictorum has the fetid smell of the 

 goat. 



Genus Unio. — This genus contains about two hun- 

 d.ed and fifty species, which, as may be supposed, 

 diti'er considerably amongst themselves in shape and 

 general appearance. The inside of the valves is gene- 

 rally brilliantly nacreous, and the hinge is furnished 

 with (often strong) cardiual teeth, and very elongated 



laminar laterals. The U. piclorum or Painter's Mus- 

 sel is extensively used for containing gold and silver 

 paint. 



Genus Damaris (=MargarUana). — This genus 

 only differs in the posterior or lateral teeth being nearly 

 obsolete. The only species of this genus is the Peari- 

 mussel, Damaris margaritifera. It is found in the 

 rivers and mountain streams of Britain, Lapland, and 

 North America. At the present day the animal is 

 used by the fishermen in Scotland as a bait. Many 

 boat-loads " are taken from the mouth of the Ythen, a 

 river not far from Aberdeen, and employed in the 

 fisheries of cod and ling, established near Peterhead."- — 

 {Johnston.) In former times, in the same country, these 

 shell-fish were used as an article of food by the na- 

 tives ; " and such is their estimation among the deintiest 

 kinds of food," says Boetius, in his account of Scotland, 

 " that they were not unwortliilie called, of old time, 

 widowes' lustes." The pearls found in this shell are 

 bright and of excellent lustre. At Perth there was an 

 extensive fishery in the river Tay, which continued 

 up to the end of last century, and which Pennant tells 

 us had from 1761 to 1764 produced pearls worth 

 £10,000. The fishery, however, we are also told, 

 was exhausted by the avarice of the undertakers, and 

 soon after ceased to be productive. In the river 

 Conway, in North Wales, excellent pearls have been 

 found ; and it is said that Sir Richard Wynn of Gwydir, 

 chamberlain to Catherine, queen of Charles II., pre- 

 sented her majesty with one taken from that river, 

 which is to this day honoured with a place in the royal 

 crown. In Ireland also a considerable fishery existed 

 as long ago as 1690. Sir Robert Reading informs us 

 tliat he had seen a pearl, taken in the county Tyrone, 

 that weighed thirty-six carats, and was valued at £40. 

 He also says " that a miller found a pearl which he 

 sold for £4 lOs. to a man that sold it for £10, who 

 disposed of it to the Lady Glenawly for £30, with whom 

 he saw it in a necklace, for which she refused £80 

 from the old Duchess of Ormond." 



Genus Barbala. — This genus has a single linear 

 tooth under tlie dorsal margin, extending the whole 

 length ; and the valves are produced at the back into a 

 thin elastic dorsal wing. i?ari()/a/)fe(<«, perhaps the 

 only species, is the famous Chinese Pearl Mussel. The 

 people of the Celestial Empire produce artificial pearls 

 in this shell, by introducing wire and other foreign 

 bodies under the mantle of the animal. In the British 

 Museum, specimens may be seen where pearls of a 

 fine lustre have been thus produced, as well as a 

 series of Httle "josses," made of metal, and which, 

 having been introduced under the mantle while the 

 animal was alive, have gradually become quite coated 

 with pearly matter. 



Genus Anodonta. — This genus has the hinge per- 

 fectly toothless. The shell is generally thin, some- 

 times of large size, oval, smooth, compressed when 

 young, but becoming ventricose by age. The spccii s 

 number about fifty, the greater number of which are 

 natives of the fresh waters of North and South Ame- 

 rica. They are very prolific ; and Mr. I. Lea, who 

 has paid great attention to the study of this family, has 

 computed that the outer gills of a female has contained 



