States, and buries itself two feet below the surface of the mud, keeping 

 its communication with the water above by means of its long siphon. 

 A large specimen is exhibited in this case with the siphons extended 

 and stuffed in their natural position. The clam of the Atlantic coast 

 lias been introduced on the Pacific coast, and it is said to be slowly 

 crowding out some of the native species of bivalves. 



"We must now pass on, and hastily glance at the two remain- 

 ing families in this case, for it will soon be closing time, when we 

 must leave the building. This family comprises the i angel wings,' 

 or ' piddock ' shells. They are all borers in mud, clay, wood, and 

 granite, although their shells are thin and fragile. It is not definitely 

 known how this boring is done, some scientists claiming that it is by 

 means of an acid solvent secreted by the animal, while others believe 

 the shell or foot to be the means employed. However this may be, 

 the mollusk and its burrow are of great interest, and worthy of much 

 study. The holes are mostly vertical and quite symmetrical, quite 

 closely fitting the form of the shell. On the coast of Devon, England, 

 the piddock, Pholas dactylus, is used for bait. In many places a large 

 number of people are employed gathering this mollusk, not only for 

 bait but for food. It is eaten well seasoned and cooked with bread 

 crumbs. The common ' angel wing ' of Florida is sold for food in 

 the markets of Havana, Cuba. The shell is curious for having two 

 accessory, spoon-shaped pieces, just beneath the umbones, which act 

 as supports for the liver of the animal. In addition to these acces- 

 sory pieces of shell the skin of the Pholas is rendered more solid and 

 rigid by the presence of many siliceous granules. It is said that the 



California piddock, 

 Parapholas califor- 

 nica, utilizes the dust 

 made by excavating 

 its burrow in build- 

 ing up a strong tube 

 to protect its si- 

 phons. The Pholas 

 emits a peculiar 



Animal of Teredo navalis. c, collar; f, foot; p, pallets; s, shell; phosphorescent 

 t, tentacles. Note the long, worm -like body of the animal. J Jo- lit when alive 



and this phosphor- 

 escence clings to it even after death. Some pelagic mollusks also possess 

 this phosphorescence. 



" The ship worm, Teredo navalis, is another borer which does an 



80 



