CLASS LAMELLIBKAKCSIATA : ORDER SIPHONATA. 251 



ORDER SIPHONATA. 



General Characteristics. — The Siphonata (siphotied) 

 include those lamellibranchiates which have respiratory tubes 

 distinctly separated from each other, and the lobes of the 

 mantle more or less united. 



Fig. kSl. 

 Fig. hSO. 



Solen ensiSy Razor Shell. 



Terido navSlis, Ship-worm. 



Solenidae (channeled) have a shell shaped like a razor- 

 handle, with a large foot, that can be turned into an awl for 

 boring into the mud, and then into a ball for pushing them- 

 selves to the surface. 



The Cardiidae (heart-shaped) put forth a foot capable 

 of distention with water introduced through an orifice near 

 the mouth. By a rotary movement of the foot thus thick- 



