CLASS LAMELLIBRA.NCHIATA. 



59 



one being nearly hidden 

 behind the other. These 

 are the gills upon one 

 side, and they consti- 

 tute what in the case 

 of the oyster is termed 

 the "beard." Two si- 

 milar gills are present 

 on the other side of the 

 body, but these are con- 

 cealed from view. To 

 the left of the gills we 

 see the heart (h), the 

 last portion of the intes- 

 tine (v), and the hinder 

 adductor (a'). To the 

 right of the giUs, below 

 the mouth, we see the 

 tongue-shaped muscular 

 organ which is known 

 as the "foot" (/). 

 Lastly, above the gills, 

 at the hinder end of the 

 body (the end opposite 

 to the mouth) we see the 

 two muscular tubes (the 

 so-called " siphons") 

 by which water is ad- 

 mitted to the interior 

 of the body, and again 

 expelled. 



We may examine the 

 internal organs c5f Mi/a 

 a little more minutely 

 by the help of the fol- 

 lowing diagram (fig. 

 25). The Mya pos- 

 sesses no distinct head, 

 but this end of the body 



a 



Fig. 24.— Anatomy of Mya, after one valve 

 and one half of the mantle have been re- 

 moved, m Cut edge of mantle ; s s The 

 breathing-tubes (siphons) cut in half; a 

 Front adductor ; a' Hinder adductor ; h 

 Heart; o Mouth, surrounded by four mem- 

 branous processes or feelers ; / Foot ; 

 Vent ; b Gills. 



