THE CLAM AND OTHER B17ALVED 8HELL-FI8H 57 

 A B 



Fig. 59. — A, the clam with its siphon extpnded: in its natural position in the 

 mud, head downwards. B, CTnio, or fresh- water mussel ; transverse section of 

 the shell, showing the position of the spring* opening* the shell; m, adductor 

 muscle. C, clam: 2, lig'ament. D. transverse view of animal of Unio (after 

 Brooks); ab, abdomen or visceral mass; a, auricles; v, ventricle; i, intestine; 

 t, glandular part of kidney ; z, non-glandular part of kidney; j/, sinus venosus; 

 ig, inner, eg^ outer, gills; m, mantle. 



