cilia, which keep up a constant motion, 

 creating currents of water, bring- thou- 

 sands of minute organisms to the clam to 

 serve as food. These little organisms, 

 many of them microscopic, are caught 

 upon the surfaces of the gills, rolled into 

 little masses, and passed into the animal's 

 mouth. Besides being food-gatherers, 

 the gills serve to keep up a circulation by 

 which fresh water is constantly brought 

 in to purify and aerate the blood and also 

 to expel the waste products. There is no 

 head in this class, and the mouth is an 

 oval slit surrounded by four lips or palp., 

 and leads almost directly into the stom- 

 ach. 



The currents of water spoken of above 

 are controlled and directed in several dif- 

 ferent ways. In attached forms, and 

 those living above the surface of the mud, 

 like the oyster, mussel and scallop, the 

 soft mantle which lines the shell is divid- 

 ed, forming- a slit nearly the whole diam- 

 eter of the shell, and the water is allowed 

 to circulate freely through the open edges 

 of the shells. But in those animals which 

 burrow in the mud, as the common little 

 neck clam, fresh water clam and quahaug, 

 this mantle is closed and prolonged pos- 

 teriorly into one double or two single 

 siphons or tubes, one being fringed with 

 little finger-like cilia and drawing in the 

 water by their motion, and the other ex- 

 pelling the water after it has circulated 

 through the animal. 



One of the most attractive families of 

 bivalve shells is the Veneridae, or venus 

 shells, in which the shelly skeleton is or- 

 namented by many bright colors, the pat- 

 terns occurring in spots, dashes, zigzag 

 lines and rays. Some varieties, as the 

 spiny venus (Cytheria lupinaria) have the 

 posterior end of the shell provided with 

 long, sharp, curved spines, and the shell 

 is also frilled in a beautiful manner. The 

 common quahaug (round or hard-shelled 

 clam), which is esteemed an article of diet 

 on the Atlantic coast, and also to some 

 extent in the interior, is a prominent 

 member of this family. The Veneridae. 

 comprise some five hundred species, 

 found throughout the world, and ranging 

 from the shore between tides to several 

 hundred fathoms in depth. 



The family Cardiidae, the heart-shells 

 or cockles, comprise some of the largest 



and most attractive of mollusks. The 

 name Cardium, signifying a heart, is 

 given them because of the close resem- 

 blance to that organ when a shell is view- 

 ed from the anterior end. These animals 

 live in sandy or muddy bays, and gener- 

 ally congregate by thousands. In En- 

 gland, the edible cockle (Cardium edule) 

 is considered quite a delicacy and thou- 

 sands are used for this purpose. In our 

 own country they are not generally eaten, 

 except by the poor in Florida and in some 

 places along the Gulf of Mexico, but the 

 waters of Florida furnish some very 

 handsome species, among them the Car- 

 dium isocardia figured on our plate, and 

 the large Cardium magnum, which grows 

 to a length of five inches and whose shell 

 is ornamented by beautiful color-patterns 

 of brown and yellow. The foot of the 

 Cardium is very peculiar, being shaped 

 like a sickle, which enables the animal to 

 pull itself along at a lively gait. A Cali- 

 fornia cockle (Liocardium elatum) grows 

 to a diameter of seven inches and would 

 furnish a meal for several people. 



In the family Tridacuidae size seems to 

 have reached its limit. Tridacena gigas, 

 found in the Indian Ocean, grows to a 

 length of nearly six feet and weighs up- 

 wards of eight hundred pounds. Tryon 

 records that a pair of these shells, weigh- 

 ing five hundred pounds, and two feet in 

 diameter, are used as benetiers in the 

 church of St. Sulpice, Paris. In some 

 parts of the Indian Ocean, where pearl 

 and sponge-fishing are carried on, this 

 clam (known as the giant clam), is a 

 source of great danger to the divers, 

 many losing their lives by being caught 

 between the great valves of the shell, by 

 either hands or feet. Many times a diver 

 has amputated his fingers, hand or foot, 

 and thus saved his life at the expense of 

 one or more of these members. 



The Tellinas (family Tellinidae) num- 

 ber among its five hundred or more spe- 

 cies some very beautiful and interesting 

 animals. They live for the most part 

 buried in sand or sandy mud and are 

 found throughout the entire world. Our 

 common Tellina radiata, familiarly 

 called sunshell, is found in Flor- 

 ida and the West Indies, and 

 a typical valve looks not unlike the 

 horizon at sunrise, the brilliant rays of 



2 o 



