520 



MOLLUSC A. 



A BLOCK OF STONE PERFORATED BY THE PHOLAS DACTTLUS. 



Si Cm 



TUBE OF THE PERFORATED 



WATERING-POT SHELL. END OF TUBE MAGNIFIED. 



ORDER 1. SIPHONATA. 



This term is derived from the Greek siphon, a curved tube. It includes several remarkable 



species. Among them is the Wa- 



g g^^^ji£3 s TERiNG-POT SiiELL, AspergUlum 



vaginifcruin : the animal in this 



THE SHIP-WORM. .'.,,. , 



case IS inclosed m a calcareous 

 tube, the anterior extremity of which is closed by a curious perforated disk; the other end is 

 ornamented with several ruffle-like bands. To this family belong the Pholadidce, the species of 



which are noted for boring into hard substances, some of them 

 making their burrows in limestone rocks, and others in wood. 

 One of the most celebrated species is the Ship-Worm, Teredo 

 navalis, a small, worm-like animal, which bores into wood sub- 

 merged in sea-water, and often does great damage to ships, and 

 to piles used for wharves and breakwaters. They bore perpendic- 

 ularly, and often in great numbers, but they never encroach upon 

 each other. When stretched out they are one to two feet long. 

 Metal sheathina: and broad-headed iron nails have been found 

 to be the best defense against these destructive pests. 



THE VENERACEA. 



These constitute a tribe of bivalve mollusks with elongated 

 siphons, and include many very elegant shells ; they generally 

 conceal themselves by burrowing, sometimes in the sand and mud, 

 and sometimes in the solid rock. The principal agent in these 

 operations is the foot. One of the most remarkable species is 

 the Ci/therea dionc, the posterior border being beset by spines, 

 and the sides furrowed with elevated lamellae. The color is of 

 a beautiful rosy purple. Found in South American seas. The C. 

 convexa is a small species, one inch and a half long, found on muddy 

 bottoms along our coasts from New Jersey to Mexico, and is called He-Clam by the fishermen. 



THE CTTHEREA DIONE. 



