ANATOMY OF THE CLAM. 



223 



the sandy bottom of the water, when the mussel is plough- 

 ing its way through the 

 sand with its tongue- 

 shaped foot, which is a 

 muscular organ attach- 

 ed to the visceral mass, 

 and is a, modification 

 of the under lip of the 

 larval mollusk, In the 

 foot is an orifice for 

 the passage m and out 

 of water, but the spurt- 

 ing of water from the 

 clam's hole, observed 

 in walking over the 

 flats, is the stream eject- 

 ed from the siphon. 

 The inflowing currents 

 of water pass from the 

 inner end of the mus- 

 cular siphon below the 

 lenticular visceral mass 

 to the mouth, which is 

 situated at the anterior 

 end of the shell, oppo- 

 site the siphon. The 

 opening is simple, un- 

 armed, without lips, 

 and often difficult to 

 detect. On each side 

 of the mouth is a pair 

 of flat, narrow-pointed 

 appendages called pal- 



"1. The digestive Ca- Yig . 155 ._ A . Ml/aarenaria wlth lts siphons extended; 



'Oil fh fl ta its n a tura l position in the mud head-end downwards. 



e B, transverse section of Cnio, showing the position of the 



maSS spring opening the shell. M, adductor muscle ; the lipa- 



' ment represented by dark mass. C, section of Mya.showng 



ting Of the position of the spring to open the shell ; L, ligament. 



D, transverse section of Unio (after Brooks) ; aft, visceral 



' Bred eX- mass ; a, auricles ; v, ventricle , i, intestine ; t, glandular 



part of kidney ; z, non-glandular part of kidney ; y, sinus 



. 3 OVai'ian venosus ; 1g, inner, eg, outer, gills ; m, mantle. 



