494 



MOLLUSKSI ACEPHALS. 



MACTRID,E. This Family contains acephala which 

 have the shell trigonal, and the hinge with two cardinal 

 teeth, besides the lateral ones. 



TELLINID.E. This Family comprises acephala which 

 have the shell compressed, and the muscular impressions 

 rounded and polished. There are three hundred living 

 and two hundred fossil species. 



Tig. 467. 



Fig. 468. Fig. 469. 



Tellina donacina. Britain. 



Tellina tenera, Say. 

 Our coast. 



Tellina tenta, Say. 

 Our coast. 



SOLENID^E, OR RAZOR-SHELL FAMILY. This Family 

 comprises acephala which have the shell much elongated 



Fig. 470. 



Solen ensis, Linn. About one third. Both shores of the Atlantic. 



and gaping at both ends. Fifty or more species are liv- 

 ing, and as many more fossil. 



MYACID^E, OR CLAM FAMILY. This Family contains 

 the common edible Clam and its allies, of which there 



Fig. 471. 



^5^ 



Fig. 472- 



Pandora obtusa. Britain. 



Mya arenaria, L. One half. 

 Northern States. 



are about one hundred living and two hundred and fifty 

 fossil species. Marine, 



