BIVALVE MOLLUSC A. 333 



have the tube covered witli a glutinated sand, mixed with small frag- 

 ments of shells of diverse colours. We know nothing of their habits, 

 and their singular forms have left naturalists in doubt as to the place 

 which should be assigned to them. It is only after having recognised 

 the existence of two valves, which were detected with great difficulty just 

 under the disc, and forming part of the sheath in which the animal is 

 encased, that it has been decided to range them with the Gastrochoe- 

 nida;, and with the shells presenting an arrangement analogous and 

 equally singular. These molluscs are, as M. Chenu says, little known, 

 rare, and hence much sought for by collectors. They are exclusively 

 exotic, the most common species being from Java. It is imported 

 into Europe by the Dutch. A third family, the Anatinidae, includes 

 such genera as Myochama, Pandora, Lyonsia, Myacites, Pholadomya, 

 Thracia, and Anatina, genera which were more important in the 

 former than in the present seas ; some, in fact, being w-holly extinct, 

 or represented, as in Pholadomya, by but one living species. A fourth 

 family, the Myacidce, including Glycimeris, which is found only in 

 America ; Panopa^a, now for the most part extinct, Thetis, Neoera, 

 C jrbula, and Mya. 



A fifth family, Solenidae, contains the Solens, w-hich under the 

 name of "razor-fish" are so abundant on the sandy shores of all parts 

 of the globe. These molluscs live with their shells buried vertically 

 in the sand, a short distance from the shore ; the hole which they 

 have hollowed, and which they never quit, sometimes attains as much 

 as two yards in depth; by means of their foot, w^hich is large, conical, 

 swollen in the middle, and pointed at its extremity, they raise them- 

 selves with great agility to the entrance of their burrow. They 

 bury themselves rapidly, and disappear on the slightest approach of 

 danger. 



When the sea retires, the presence of the Solen is indicated by a 

 small orifice in the sand, whence escape at intervals bubbles of air. 

 In order to attract them to the surface, the fishermen throw into the 

 hole a pinch of salt ; immediately the sand becomes stirred, and the 

 animal presents itself just above the point of its shell. It must be 

 seized at once, for it disappears again very quickly, and no renewed 

 efforts will bring it to the surface a second time. Its retreat is 

 commonly cut short by a knife being passed below it ; for it burrows 

 into the ground with such velocity that it is difficult to capture it with 

 the hands alone. 



This shell has by some been compared to a knife-handle ; by 

 others to a razor, which has become its popular name. It is a thin, 

 transparent, long, and slender equivalved bivalve, with parallel edges, 



